Shark feature (3)
I believe the answer is:
fin
'shark feature' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for fin that I've seen before include "Fish propeller; end (Fr.)" , "A fish uses it to steer itself" , "Swimmer's flipper" , "Paddle-like organ" , "For movement and balance in fish" .)