See old lover (5)
I believe the answer is:
romeo
'lover' is the definition.
(I've seen this before)
'see old' is the wordplay.
'see' becomes 'rome' (the Holy See or See of Rome is home to the pope).
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'rome'+'o'='ROMEO'
(Other definitions for romeo that I've seen before include "Famous lover" , "Lover; R (radio comms.)" , "Tragic lover" , "A great lover" , "Ladies' man" .)