Shrewd bargaining by Arabian doing a bit of dealing (5,7)
I believe the answer is:
horse trading
'shrewd bargaining' is the definition.
(I've seen this in another clue)
'bit of dealing' is the wordplay.
'bit of' becomes 'horse' (I can't explain this - if you can you should believe this answer much more).
'dealing' becomes 'trading' (I've seen this before).
'horse'+'trading'='HORSE-TRADING'
'by arabian doing a' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for horse trading that I've seen before include "Hard bargaining (at yearling sales?)" , "part of stable business?" , "Ordering hats (anag) -- ordering quadrupeds?" , "Hard and shrewd bargaining" .)