Rogue bishop to go without protection (10)
I believe the answer is:
blackguard
'rogue' is the definition.
(I've seen this before)
'bishop to go without protection' is the wordplay.
'bishop' becomes 'b' (abbreviation used in chess).
'to go without' becomes 'lack'.
'protection' becomes 'guard' (I've seen this before).
'b'+'lack'+'guard'='BLACKGUARD'
(Other definitions for blackguard that I've seen before include "Dishonourable man" , "Contemptible scoundrel" , "miscreant" , "Cad" , "rogue" .)