Turn-on (see models privately) (5,4)
I believe the answer is:
entre nous
'privately' is the definition.
('between ourselves' in French)
'turn-on see models' is the wordplay.
'models' indicates an anagram.
'turn'+'on'+'see'='turnonsee'
'turnonsee' with letters rearranged gives 'ENTRE NOUS'.
(Other definitions for entre nous that I've seen before include "in secret" , "in confidence" , "private" , "Between ourselves (French)" .)