Billy, perhaps, though Charlie has one (3)
I believe the answer is:
can
'billy' is the definition.
(I've seen this before)
'charlie has one' is the wordplay.
'charlie' becomes 'C' (phonetic alphabet).
'has' is a charade indicator (letters next to each other).
'one' becomes 'an' (an apple is one apple).
'c'+'an'='CAN'
'perhaps though' acts as a link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for can that I've seen before include "prison" , "toilet" , "Is able; container" , "Cooler" , "has power" .)