Delete everything after the first space in Notepad++

If the data in the first column never contains a space, you can use a regular expression find and replace to get what you want.

In regular expression mode, search for:

^([^ ]*).*
And replace with

\1


Before
70.97.110.40    159 ms          [n/a]                   21
70.97.117.177   134 ms          [n/a]                   21
70.97.120.10    75 ms           [n/a]                   21

After
70.97.110.40
70.97.117.177
70.97.120.10