Did You noticed that #2 reply has three (3) different variations?
Did You think second variation? It makes same as Your 'have to'.
Did You try to do third variation? It seems to give the most nearest result for Your 'have to'.
You should try to record it ...
1) make sure that Your 1.csv-file is closed
2) open a new Excel-file
3) Tools > Marcos > Record New Macro ...
4) Give a name for Macro
5) Open Your named 1.csv-file
6) Select from sheet the left top corner to get all cells selected
7) Use mouse's right button to get menu
8) Select 'Clear Contents'
9) Press Ctrl+S to save it
10) Close that 1.csv-file
11) Stop Marco Recording