Greek character wasted pun on model (3-2)
I believe the answer is:
pin-up
'model' is the definition.
(pin-up is a kind of model)
'greek character wasted pun on' is the wordplay.
'greek character' becomes 'pi' (letter from the Greek alphabet**).
'wasted' is an anagram indicator.
'on' is an insertion indicator (as in clothing \'on\' a person).
'pun' with letters rearranged gives 'nup'.
'pi' placed into 'nup' is 'PIN-UP'.
(Other definitions for pin-up that I've seen before include "Sexy model" , "Alluring poster" , "Attractive figure" , "Attach (to a notice board)" , "Poster of an attractive person" .)