The old man, a holy person in history (4)
I believe the answer is:
past
'history' is the definition.
(I've seen this before)
'the old man a holy person' is the wordplay.
'the old man' becomes 'pa' ('pa' can be a synonym of 'old man'**).
'a holy person' becomes 'st' (I've seen this in other clues).
'pa'+'st'='PAST'
'in' acts as a link.
(Other definitions for past that I've seen before include "over and done with" , "historical times" , "Beyond" , "Ended" , "Bygone" .)