Ugly creature of folklore (5)
I believe the answer is:
troll
'ugly creature of folklore' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for troll that I've seen before include "Fish by pulling a hook, line and sinker" , "who's stirring on-line" , "unwanted contributor to site?" , "Online annoyance" , "Internet provoker; ugly being" .)