Fish in nasty drains eaten for starter? (7)
I believe the answer is:
sardine
'fish' is the definition.
(sardine is a kind of fish)
'nasty drains eaten for starter?' is the wordplay.
'nasty' indicates anagramming the letters.
'for starter?' says to take the initial letters (I've seen 'for starters' mean this).
The first letter of 'eaten' is 'e'.
'drains' anagrammed gives 'sardin'.
'sardin'+'e'='SARDINE'
'in' is the link.
(Other definitions for sardine that I've seen before include "A diner's small fish" , "Swimmer" , "Rinsed a (anag) - fish" , "Small pilchard" , "Fish in tin?" .)