Leaving university, compulsion becomes habit (5)
I believe the answer is:
dress
'habit' is the definition.
(I've seen this in another clue)
'leaving university compulsion' is the wordplay.
'leaving' is a deletion indicator.
'university' becomes 'U' (abbreviation as in UMass).
'compulsion' becomes 'duress' (as in doing something under duress).
'duress' with 'u' taken out is 'DRESS'.
'becomes' is the link.
(Other definitions for dress that I've seen before include "This woman might slip on" , "Costume" , "items to wear" , "Clothing - groom" , "clean > bandage" .)