How to Clear field from text?

Hello!
Does anyone know how you can clean a text field?

A text field where? On a custom page? Please take a bit more time to provide useful information when posting questions!

On customized page using nsDialogs::CreateControl EDIT

I assume by clear you mean just make it empty? Just do

${NSD_SetText} $myTextbox ""

Something like this

# Test Read File
Name "NSIS Test" 
Caption "NSIS Test" 
OutFile "NSIS Test.exe" 
InstallDir "$TEMP\NSIS Test" 
# COMPRESS 
SetCompressor lzma 
# RUN 
RequestExecutionLevel user 
# INCLUDES 
!include "MUI2.nsh" 
!include "nsDialogs.nsh" 
!include "FileFunc.nsh" 
!include "WinMessages.nsh" 
# Icon & Stye 
BrandingText /TRIMRIGHT " " 
Page custom Page.Custom.Test /ENABLECANCEL  
Page instfiles  
# LANGUAGES 
!insertmacro MUI_LANGUAGE "English" # first language 
Function Page.Custom.Test 
  var /GLOBAL Dialog
  var /GLOBAL Btn_Read
  var /GLOBAL Path.READ
  var /GLOBAL Lbl.Add
  var /GLOBAL PATH.FILE
  var /GLOBAL Btn_Add
  GetDlgItem $0 $HWNDPARENT 1 
  ShowWindow $0 ${SW_HIDE} 
  GetDlgItem $0 $HWNDPARENT 2 
  ShowWindow $0 ${SW_HIDE} 
  GetDlgItem $0 $HWNDPARENT 3 
  ShowWindow $0 ${SW_HIDE} 
  GetDlgItem $0 $HWNDPARENT 1990 
  ShowWindow $0 ${SW_HIDE} 
  GetDlgItem $0 $HWNDPARENT 1991 
  ShowWindow $0 ${SW_HIDE} 
  GetDlgItem $0 $HWNDPARENT 1992 
  ShowWindow $0 ${SW_HIDE} 
  System::Call "user32::SetWindowPos(i$HWNDPARENT,i,i,i,i 632,i 466,i 0x16)"  
  nsDialogs::Create /NOUNLOAD 1044  
  Pop $Dialog  
  ${If} $Dialog == error  
   Abort  
  ${EndIf}  
  System::Call "user32::MoveWindow(i$Dialog,i0,i0,i 632,i 466,i0)"  
  SetCtlColors $Dialog 0xbbbbbb 0x323232
  # ...:: ADD FILE ::... #
  nsDialogs::CreateControl STATIC 0x40000000|0x10000000|0x04000000|0x00000100 0x00000020 2% 2% 165u 15u "Add Your File:"
  pop $Lbl.Add
  SetCtlColors $Lbl.Add 0xbbbbbb 0x323232
  CreateFont $0 "MV Boli" "12" "100"
  SendMessage $Lbl.Add ${WM_SETFONT} $0 0 
  nsDialogs::CreateControl /NOUNLOAD EDIT 0x40000000|0x10000000|0x04000000|0x00010000|0x00000080 0 2% 7% 79% 15u ""
  Pop $PATH.FILE
  CreateFont $0 "MV Boli" "12" "100"
  SendMessage $PATH.FILE ${WM_SETFONT} $0 0 
  SetCtlColors $PATH.FILE 0xbbbbbb 0x424242
  # ...:: BTN ADD ::... #
  nsDialogs::CreateControl /NOUNLOAD BUTTON 0x40000000|0x10000000|0x04000000|0x00010000 0 82% 7% 65u 15u ""
  Pop $Btn_Add
  Strcpy $1 $Btn_Add
  GetFunctionAddress $3 "on.Click.Add"
  nsDialogs::onClick $1 $3
  SetCtlColors $Btn_Add 0xbbbbbb 0x323232
  CreateFont $0 "MV Boli" "10" "400"
  SendMessage $Btn_Add ${WM_SETFONT} $0 0 
  SendMessage $Btn_Add '${WM_SETTEXT}' '0' "STR:Add ..."
  # ...:: READ LOCATION ::... #
  nsDialogs::CreateControl /NOUNLOAD EDIT 0x40000000|0x10000000|0x04000000|0x00010000|0x00000080|0x00000004|0x00200000|0x00100000|0x00000800 0 2% 15% 96% 190u "" # 0x00000100|0x00000200
  Pop $PATH.READ
  CreateFont $0 "MV Boli" "12" "100"
  SendMessage $PATH.READ ${WM_SETFONT} $0 0 
  SetCtlColors $PATH.READ 0xbbbbbb 0x424242
  # ...:: BTN READ ::... #
  nsDialogs::CreateControl /NOUNLOAD BUTTON 0x40000000|0x10000000|0x04000000|0x00010000 0 145u 245u 120u 18u "Read Now ..." ; Read
  Pop $Btn_Read
  StrCpy $1 $Btn_Read
  GetFunctionAddress $3 "On.Click.Read"
  nsDialogs::onClick $1 $3
  SetCtlColors $Btn_Read 0xbbbbbb 0x323232
  CreateFont $0 "MV Boli" "12" "100"
  SendMessage $Btn_Read 0x0030 $0 0
  nsDialogs::Show
FunctionEnd
# ...:: ADD ::... #
var /global MYFILES
Function "on.Click.Add"
  nsDialogs::SelectFileDialog "open" "C:\" "All Files|*.txt;*.ini;*.pls;*.m3u;*.bat;*.nsi;*.nsh;*.dat;*.htm;*.html;*.css;*.js;*.xml;*.rtf;*.log;*.reg;*.lng;*.data;*.json|*.*"
  Pop $0
  StrCpy $MYFILES "$0"
    ${NSD_SetText} $PATH.FILE "$MYFILES"
    SendMessage $PATH.READ ${WM_SETTEXT} 0 "STR: "
FunctionEnd
Function "On.Click.Read"
FileOpen $4 "$MYFILES" r
loop:
    FileRead $4 $1
    SendMessage $PATH.READ ${EM_REPLACESEL} 0 "STR:$1"
    IfErrors +1 loop
FileClose $4
FunctionEnd
Section "Main" SEC01
SectionEnd
Function .onGUIEnd
FunctionEnd