Blessing bishop with nothing on (4)
I believe the answer is:
boon
'blessing' is the definition.
(synonyms)
'bishop with nothing on' is the wordplay.
'bishop' becomes 'B' (chess abbreviation).
'with' is a charade indicator (letters next to each other).
'nothing' becomes 'O' (looks like zero - 0).
'b'+'o'+'on'='BOON'
(Other definitions for boon that I've seen before include "Beneficial thing" , "Blessing - sort of companion?" , "Benefaction" , "A benefit, goes with blessing" , "Favour, request" .)