A priest, self-centred, has fun (5)
I believe the answer is:
revel
'fun' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
'a priest self-centred' is the wordplay.
'a priest' becomes 'rev' (short for reverend).
'centred' says to take the centre.
The middle letters of 'self' are 'el'.
'rev'+'el'='REVEL'
'has' acts as a link.
Can you help me to learn more?
(Other definitions for revel that I've seen before include "Make merry, whoop it up" , "party" , "Rejoice" , "Be festive, enjoy" , "Riotous feast" .)