Chill student put hinge askew (7,2)
I believe the answer is:
lighten up
'chill' is the definition.
(I've seen this before)
'student put hinge askew' is the wordplay.
'student' becomes 'L' (as in L-plates for learner drivers).
'askew' indicates an anagram.
'put'+'hinge'='puthinge'
'puthinge' anagrammed gives 'ightenup'.
'l'+'ightenup'='LIGHTEN UP'
(Other definitions for lighten up that I've seen before include "Chill" , "Relax!" , "Plug in the fire" , "Unwind" .)