Clinging crustacean (8)
I believe the answer is:
barnacle
'clinging crustacean' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for barnacle that I've seen before include "Crustacean that attaches to a submerged surface" , "One that sticks" , "Clinging sort" , "Marine crustacean (attaching to rocks, ships etc.)" , "type of goose" .)