The perfect fashion student (5)
I believe the answer is:
model
'the perfect' is the definition.
(I've seen this before)
'fashion student' is the wordplay.
'fashion' becomes 'mode' ('mode' can be a synonym of 'fashion').
'student' becomes 'l' (as in L-plates for learner drivers**).
'mode'+'l'='MODEL'
(Other definitions for model that I've seen before include "Artist's sitter" , "She exhibits clothes on the catwalk" , "Possibly the last" , "(Person functioning as) example" , "Representative example" .)