Bishop getting uncomfortable becomes spiteful (6)
I believe the answer is:
bitchy
'spiteful' is the definition.
(I've seen this before)
'bishop getting uncomfortable' is the wordplay.
'bishop' becomes 'b' (abbreviation used in chess).
'getting' is a charade indicator (letters next to each other).
'uncomfortable' becomes 'itchy'.
'b'+'itchy'='BITCHY'
'becomes' acts as a link.
(Other definitions for bitchy that I've seen before include "Unpleasant and spiteful like female dog" , "malicious" , "Catty" , "Speaking spitefully in manner of female canine" .)