Small spiny fish (11)
I believe the answer is:
stickleback
'small spiny fish' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for stickleback that I've seen before include "Small pugnacious fish -- kick Cable St (anag)" , "Spined tiddler" , "Small spiny fish" , "Swimmer" .)