Uncle's not in credit - so be off! (5)
I believe the answer is:
scram
'be off' is the definition.
(I've seen this before)
'uncle's not in credit' is the wordplay.
I cannot quite understand how this works, but
'credit' could be 'cr' (abbreviation) and 'cr' is located in the answer.
'uncle' could be 'sam' (Uncle Sam is an example) and 'sam' is found in the remaining letters.
This accounts for all the letters.
This may be the basis of the clue (or it may be nonsense).
'so' is the link.
Can you help me to learn more?
(Other definitions for scram that I've seen before include "In slang, go away and beat it" , "on your bike!" , "beat hasty retreat" , "Skedaddle!" , "Make oneself scarce" .)