Spotted after a bishop avoided voting (9)
I believe the answer is:
abstained
'avoided voting' is the definition.
'spotted after a bishop' is the wordplay.
'spotted' becomes 'stained' ('stain' can be a synonym of 'spot').
'after' means one lot of letters go next to another.
'bishop' becomes 'B' (abbreviation used in chess).
'a'+'b'='ab'
'stained' after 'ab' is 'ABSTAINED'.
(Other definitions for abstained that I've seen before include "went on the wagon" , "kept dry" , "was non-committal" , "chose not to vote" , "avoided port?" .)