Popular journal one catholic finds 'lifeless' (9)
I believe the answer is:
inorganic
'lifeless' is the definition.
'popular journal one catholic' is the wordplay.
'popular' becomes 'in'.
'journal' becomes 'organ' (I've seen this before).
'one' becomes 'i' (Roman numeral).
'catholic' becomes 'c' (abbreviation as in RC for Roman Catholic).
'in'+'organ'+'i'+'c'='INORGANIC'
'finds' is the link.
(Other definitions for inorganic that I've seen before include "Not of animal/vegetable origin" , "Not deriving from living matter" , "artificial" , "Man-made" , "Not derived from living matter" .)