Models posed infrequently (6)
I believe the answer is:
seldom
'infrequently' is the definition.
(I've seen this in another clue)
'models posed' is the wordplay.
'posed' is an anagram indicator (I've seen 'pose' mean this (the letters must be re-posed into a new order)).
'models' anagrammed gives 'SELDOM'.
(Other definitions for seldom that I've seen before include "Not 21" , "Alluvium" , "Not often, infrequently" , "Models (anag)" , "Only occasionally" .)