More than one model is accepting contract (6)
I believe the answer is:
ideals
'more than one model' is the definition.
(ideal is a kind of model)
'is accepting contract' is the wordplay.
'accepting' means one lot of letters goes inside another.
'contract' becomes 'deal' (I've seen this before).
'is' enclosing 'deal' is 'IDEALS'.
(Other definitions for ideals that I've seen before include "Highest standards, model objectives" , "Fine aspirations for ladies" , "Morals" , "Moral value" , "Standards to be aimed at" .)