Old boy, recent monastic dedicatee (6)
I believe the answer is:
oblate
'monastic dedicatee' is the definition.
(I've seen this before)
'old boy recent' is the wordplay.
'old boy' becomes 'OB' (abbreviation for a private school 'old boy').
'recent' becomes 'late' (similar in meaning).
'ob'+'late'='OBLATE'
(Other definitions for oblate that I've seen before include "Of sphere, flattened at poles" , "Of spheroid, flattened at the ends" , "a religious person" , "Of spheroid, flattened at the poles" , "Squashed (sphere)" .)