Son snubbed fish, going back for other seafood (7)
I believe the answer is:
scallop
'seafood' is the definition.
(scallop is a kind of seafood)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for scallop that I've seen before include "one may be in one's shell" , "Bivalve mollusc with fan-shaped shell" , "Bivalve with radiating ridges on shell" , "Shellfish that's also plc" , "Marine bivalve" .)