Crudely paint bishop, covered by diamonds and gold (4)
I believe the answer is:
daub
'crudely paint' is the definition.
'daub' can be an answer for 'paint' (thesaurus). I'm unsure of the 'crudely' bit.
'bishop covered by diamonds and gold' is the wordplay.
'bishop' becomes 'B' (chess abbreviation).
'covered by' means one lot of letters go next to another (on top of in a down clue).
'diamonds' becomes 'd' (abbreviation in bridge say).
'and' is a charade indicator (letters next to each other).
'gold' becomes 'Au' (Au is the chemical symbol for gold).
'd'+'au'='dau'
'b' after 'dau' is 'DAUB'.
Can you help me to learn more?
(Other definitions for daub that I've seen before include "Smear; plaster" , "Smear; bad painting" , "coat casually" , "Amateurish painting" , "Plaster; paint crudely" .)