Models working rarely (6)
I believe the answer is:
seldom
'rarely' is the definition.
(I know that rarely can be written as seldom)
'models working' is the wordplay.
'working' indicates an anagram.
'models' with letters rearranged gives 'SELDOM'.
(Other definitions for seldom that I've seen before include "Alluvium" , "Infrequent" , "Only occasionally" , "Once in a blue moon" , "Models (anag)" .)