Try charm to impress very old university (9)
I believe the answer is:
endeavour
'try' is the definition.
(endeavouring is a kind of trying)
'charm to impress very old university' is the wordplay.
'charm' becomes 'endear' (I've seen this before**).
'to impress' is an insertion indicator (impress can mean enlist or recruit).
'very' becomes 'v' (abbreviation).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'university' becomes 'u'.
'v'+'o'+'u'='vou'
'endear' enclosing 'vou' is 'ENDEAVOUR'.
(Other definitions for endeavour that I've seen before include "Try hard (to achieve)" , "The first handle inspector has" , "hard work" , "Aim" , "Try - Captain Cook's vessel" .)