One who copies head of Cardiff University's resumé (6)
I believe the answer is:
apercu
'resume' is the definition.
(apercu is a kind of resume)
'one who copies head of cardiff university's' is the wordplay.
'one who copies' becomes 'aper' (I've seen this in another clue).
'head of' says to take the initial letters.
The first letters of 'cardiff universitys' is 'cu'.
'aper'+'cu'='APERCU'
(Other definitions for apercu that I've seen before include "what's observed" , "Illuminating comment, race up (anag.)" , "9 [WHATS THE POINT]" , "Illuminating or entertaining point (from French)" , "Precis, brief outline" .)