Not now an official papal residence? It was once (7)
I believe the answer is:
lateran
'official papal residence? it was once' is the definition.
I can't tell whether this definition defines the answer.
'not now an' is the wordplay.
'not now' becomes 'later' (I've seen this in another clue).
'later'+'an'='LATERAN'
Can you help me to learn more?
(Other definitions for lateran that I've seen before include "St John --, church in Rome" , "of a Roman cathedral" , "Old council" , "papal church" , "Of a particular Roman district; an alert, anag." .)