A Catholic area of much activity where records are kept (7)
I believe the answer is:
archive
'where records are kept' is the definition.
(records are kept in an archive)
'a catholic area of much activity' is the wordplay.
'catholic' becomes 'RC' (Roman Catholic).
'area of much activity' becomes 'hive' (as in 'a hive of activity').
'a'+'rc'+'hive'='ARCHIVE'
(Other definitions for archive that I've seen before include "Document depository" , "Collection of documents of an institution or community" , "Data repository" , "Record repository" , "Store for historic records" .)