The holy father came in with the prior (8)
I believe the answer is:
previous
'the prior' is the definition.
(I've seen this in another clue)
'the holy father came in' is the wordplay.
'the holy' becomes 'pious'.
'father' becomes 'rev' (I've seen this in other clues).
'came in' indicates putting letters inside.
'pious' going around 'rev' is 'PREVIOUS'.
'with' is the link.
(Other definitions for previous that I've seen before include "earlier convictions" , "Foregoing" , "Earlier, occasion say" , "Overhasty; existing earlier" , "form" .)