Little plastic models (6)
I believe the answer is:
seldom
'little' is the definition.
(thesaurus)
'plastic models' is the wordplay.
'plastic' indicates anagramming the letters (plastic can mean easily moulded).
'models' is an anagram of 'SELDOM'.
(Other definitions for seldom that I've seen before include "Once in a blue moon" , "Models (anag)" , "Not 21" , "Not often, infrequently" , "Not very often, rarely" .)