Model, leg in the air? (3-2)
I believe the answer is:
pin-up
'model' is the definition.
(pin-up is a kind of model)
'leg in the air?' is the wordplay.
'leg' becomes 'pin' (pin is a kind of leg).
'in the air?' becomes 'up'.
'pin'+'up'='PIN-UP'
(Other definitions for pin-up that I've seen before include "Alluring poster" , "Cover girl" , "(Picture of) sexually attractive person" , "Sexy model" , "Poster of an attractive person" .)