Spot, so we hear, for fish (6)
I believe the answer is:
plaice
'fish' is the definition.
(plaice is a kind of fish)
'spot so we hear' is the wordplay.
'spot' becomes 'place' (synonyms).
'so we hear' indicates a 'sounds like' (homophone) clue.
'place' sounds like 'PLAICE'.
'for' acts as a link.
(Other definitions for plaice that I've seen before include "N. Atlantic flatfish" , "Swimmer" , "Large flatfish" , "A succulent flat-fish" , "Position the fish, we hear" .)