University official, American, in study (4)
I believe the answer is:
dean
'university official' is the definition.
(I've seen this before)
'american in study' is the wordplay.
'american' becomes 'a' (common abbreviation - e.g. in organisation names).
'in' means one lot of letters goes inside another.
'study' becomes 'den' (I've seen this before).
'a' placed within 'den' is 'DEAN'.
(Other definitions for dean that I've seen before include "Senior academic administrator" , "College officer" , "Cathedral cleric" , "Administrator of a college department" , "Senior church official" .)