Fin (7)
I believe the answer is:
flipper
'fin' is the definition.
(I know that fin can be written as flipper)
This is the entire clue.
(Other definitions for flipper that I've seen before include "Limb of a seal" , "feature of dolphin?" , "Flat broad limb of aquatic animals" , "Shoe for swimming" , "provision for diver" .)