Minister's aide tormented a co-ed head (9)
I believe the answer is:
deaconess
'minister's aide' is the definition.
(a deacon or deaconess assists a priest)
'tormented a co-ed head' is the wordplay.
'tormented' indicates anagramming the letters.
'head' becomes 'ness' (ness is a headland).
'a'+'co'+'ed'='acoed'
'acoed' is an anagram of 'deaco'.
'deaco'+'ness'='DEACONESS'
(Other definitions for deaconess that I've seen before include "Female lay official of the church" , "Minister" .)