Money for fish is about right (5)
I believe the answer is:
brass
'money' is the definition.
(I've seen this before)
'fish is about right' is the wordplay.
'fish' becomes 'bass' (bass is a kind of fish**).
'is about' means one lot of letters goes inside another.
'right' becomes 'r' (common abbreviation).
'bass' enclosing 'r' is 'BRASS'.
'for' acts as a link.
(Other definitions for brass that I've seen before include "An alloy; part of orchestra" , "neck" , "Ready" , "Boldness" , "Common alloy" .)