Back prohibition by a Middle Easterner (4)
I believe the answer is:
arab
'middle easterner' is the definition.
(I've seen this in another clue)
'back prohibition by a' is the wordplay.
'back prohibition' becomes 'rab' (I can't explain this - if you can you should give a lot more credence to this answer).
'by' is a charade indicator (letters next to each other).
'rab' after 'a' is 'ARAB'.
Can you help me to learn more?
(Other definitions for arab that I've seen before include "Fine horse breed" , "race" , "Saudi, perhaps - breed of horse" , "Mount" , "Person from the Middle East, say" .)