Represented as saline marine mollusc (3,5)
I believe the answer is:
sea snail
'marine mollusc' is the definition.
(I've seen this before)
'represented as saline' is the wordplay.
'represented' is an anagram indicator.
'as'+'saline'='assaline'
'assaline' anagrammed gives 'SEA-SNAIL'.
(Other definitions for sea snail that I've seen before include "wet crawler" , "Creeping marine creature with a spiral shell" , "Spiral-shelled marine mollusc" .)