Associate uses alternate card and only withdraws fifty (5)
I believe the answer is:
crony
'associate' is the definition.
(a crony is a friend or associate)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for crony that I've seen before include "Intimate companion" , "mate" , "China" , "Sidekick" , "Close companion" .)