A graduate with zest? Incredible! (7)
I believe the answer is:
amazing
'incredible' is the definition.
(I've seen this in another clue)
'a graduate with zest?' is the wordplay.
'graduate' becomes 'MA' (abbreviation for Master of Arts).
'with' means one lot of letters go next to another.
'zest?' becomes 'zing' (I've seen this before).
'a'+'ma'+'zing'='AMAZING'
(Other definitions for amazing that I've seen before include "Hymn that 'sav'd a wretch like me'?" , "Prodigious" , "Stunning, surprising" , "Causing great surprise" , "Very impressive" .)