Please TEST this FIRST in a COPY of your workbook (always make a backup copy before trying new code, you never know what you might lose).
1. Copy the below code, by highlighting the code and pressing the keys CTRL + C
2. Open your workbook
3. Press the keys ALT + F11 to open the Visual Basic Editor
4. Press the keys ALT + I to activate the Insert menu
5. Press M to insert a Standard Module
6. Where the cursor is flashing, paste the code by pressing the keys CTRL + V
7. Press the keys ALT + Q to exit the Editor, and return to Excel
8. To run the macro from Excel, open the workbook, and press ALT + F8 to display the Run Macro Dialog. Double Click the macro's name to Run it.
Before you use the macro with Excel 2007 or newer, save your workbook, Save As, a macro enabled workbook with the file extension .xlsm
Dim c As Range, s
Application.ScreenUpdating = False
For Each c In Range("A1", Range("A" & Rows.Count).End(xlUp))
If InStr(c, Chr(10)) > 0 Then
s = Split(c, Chr(10))
c = s(0)
Application.ScreenUpdating = True
Then run the DeleteSecondTextLine macro.
Have a great day,