Troll using some 'gammon' stereotypes (7)
I believe the answer is:
monster
'troll' is the definition.
(thesaurus)
'some gammon stereotypes' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'MONSTER' can be found hidden inside 'gammon stereotypes'.
'using' is the link.
(Other definitions for monster that I've seen before include "Strange mentors for the imaginary creature" , "Hideous animal" , "Stupendous" , "Gigantic" , "On terms (anag) - cruel person" .)