Overcharge for coat (6)
I believe the answer is:
fleece
I believe this clue is a double definition.
'overcharge' is the first definition.
('fleece' can be a synonym of 'overcharge')
'coat' is the second definition.
(fleece is a kind of coat)
'for' acts as a link.
(Other definitions for fleece that I've seen before include "What shearer has to" , "A target for Jason" , "A sheep's woolly coat" , "Charge way over the odds" , "Rook; animal's coat" .)