A French hack abides, impartial (8)
I believe the answer is:
unbiased
'impartial' is the definition.
(similar in meaning)
'a french hack abides' is the wordplay.
'a french' becomes 'un' ('a' in French).
'hack' indicates anagramming the letters (I've seen 'hacking' mean this).
'abides' is an anagram of 'biased'.
'un'+'biased'='UNBIASED'
(Other definitions for unbiased that I've seen before include "Not prejudiced or influenced" , "without side" , "fair" , "Not favouring one side or the other" , "Not prejudiced or partisan" .)