Give about £50 just to be friendly (5)
I believe the answer is:
pally
'to be friendly' is the definition.
('pally' can be similar in meaning to 'friendly')
'give about ps50' is the wordplay.
'give' becomes 'ply' (plying is a kind of giving).
'about' is an insertion indicator.
'ps50' becomes 'al' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'ply' enclosing 'al' is 'PALLY'.
'just' is the link.
This may not be correct. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for pally that I've seen before include "Thick" , "Chummy" , "On friendly terms" , "China may be so" , "Close, friendly" .)