Money found right inside fish (5)
I believe the answer is:
brass
'money' is the definition.
(I've seen this before)
'right inside fish' is the wordplay.
'right' becomes 'r' (common abbreviation).
'inside' means one lot of letters goes inside another.
'fish' becomes 'bass' (bass is a kind of fish**).
'r' put into 'bass' is 'BRASS'.
'found' acts as a link.
(Other definitions for brass that I've seen before include "Alloy (associated with muck)" , "Boldness" , "Metal - cheek" , "Impertinence" , "some players!" .)