Sandier sort of fish (7)
I believe the answer is:
sardine
'fish' is the definition.
(sardine is a type of fish)
'sandier sort' is the wordplay.
'sort' indicates anagramming the letters.
'sandier' with letters rearranged gives 'SARDINE'.
'of' acts as a link.
(Other definitions for sardine that I've seen before include "FRENCH FISH" , "Small fish, usually canned" , "Fish (often tinned)" , "Stonefish OR? Stone" , "Small pilchard" .)