Is main credit somehow showing bias? (12)
I believe the answer is:
discriminate
'bias?' is the definition.
(to discriminate is to show a bias)
'is main credit somehow' is the wordplay.
'somehow' indicates an anagram.
'is'+'main'+'credit'='ismaincredit'
'ismaincredit' anagrammed gives 'DISCRIMINATE'.
'showing' acts as a link.
(Other definitions for discriminate that I've seen before include "Show taste" , "Tell apart" , "Use taste and judgment (or prejudice)" , "Unjustly treat a group as different" , "Recognise a distinction" .)