As a friend, perhaps, Pearl's finished with Joe (4)
I believe the answer is:
girl
'as a friend' is the definition.
I can't tell whether this definition defines the answer.
'pearl's finished with joe' is the wordplay.
'pearl's finished' becomes 'rl' (I can't justify this - if you can you should give a lot more credence to this answer).
'with' is a charade indicator (letters next to each other).
'joe' becomes 'GI' (GI Joe).
'rl' put after 'gi' is 'GIRL'.
'perhaps' acts as a link.
Can you help me to learn more?
(Other definitions for girl that I've seen before include "Young lady" , "A young female" , "One of 8 [LASSES]" , "Lass" , "See 5" .)