Return of academics keeping year for religious meeting (5)
I believe the answer is:
synod
'religious meeting' is the definition.
(type of gathering of clergy)
'return of academics keeping year' is the wordplay.
'return of' says the letters should be written in reverse.
'academics' becomes 'dons' (I've seen this before).
'keeping' means one lot of letters goes inside another.
'year' becomes 'y'.
'dons' enclosing 'y' is 'donys'.
'donys' back-to-front is 'SYNOD'.
'for' acts as a link.
(Other definitions for synod that I've seen before include "group of clergymen" , "Church assembly" , "council meeting" , "Ecclesiastical council" , "Ecumenical council" .)