Jacket for old university student in enclosure (7)
I believe the answer is:
cagoule
'jacket' is the definition.
(I know that cagoule is a type of jacket)
'old university student in enclosure' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'university' becomes 'u' (abbreviation for university).
'student' becomes 'l' (as in L-plates for learner drivers).
'in' is an insertion indicator.
'enclosure' becomes 'cage' (cage is a kind of enclosure).
'o'+'u'+'l'='oul'
'oul' going within 'cage' is 'CAGOULE'.
'for' is the link.
(Other definitions for cagoule that I've seen before include "coat" , "hooded top" , "Hooded jacket" , "Waterproof garment" , "Hiker's waterproof" .)