Monster forgeries displayed regularly (4)
I believe the answer is:
ogre
'monster' is the definition.
(fairy tale monster)
'forgeries displayed regularly' is the wordplay.
'displayed regularly' means one should take alternating letters.
The alternating letters of 'forgeries' are 'OGRE'.
(Other definitions for ogre that I've seen before include "Man-eating giant of folklore" , "Terrifying man" , "Brute" , "Ergo (anag.)" , "Fierce giant" .)