Proprietor in Bow further over the hill? (5)
I believe the answer is:
older
This clue is a double definition.
'proprietor in bow' is the first definition.
('holder' - thesaurus - said with a cockney accent, dropping the 'H')
'further over the hill?' is the second definition.
('over the hill' can informally mean old or aging)
(Other definitions for older that I've seen before include "Getting on" , "More advanced in point of time" , "as we all will be tomorrow" , "Of greater age (O, not E)" , "More senior" .)