Plant; mollusc (10)
I believe the answer is:
periwinkle
I believe this clue is a double definition.
'plant' is the first definition.
(periwinkle is a kind of plant)
'mollusc' is the second definition.
(I know that periwinkle is a type of sea snail)
(Other definitions for periwinkle that I've seen before include "Plant; mollusc" , "Tiny seafood item - purplish-blue shade" , "Plant with five-petalled flowers" , "Evergreen creeper" , "This plant may be poisonous" .)