Dwarf fish (5)
I believe the answer is:
troll
I believe this clue is a double definition.
'dwarf' is the first definition.
(I've seen this before)
'fish' is the second definition.
(thesaurus)
(Other definitions for troll that I've seen before include "Fish by pulling a hook, line and sinker" , "Fairytale monster" , "Supernatural cave-dweller" , "Fish by trailing a baited line" , "Fish - cave-elf" .)