Payment about to arrive with enclosures inside (10)
I believe the answer is:
recompense
'payment' is the definition.
(recompense is a kind of payment)
'to arrive with enclosures inside' is the wordplay.
'to' becomes 're' (I can't explain this - if you can you should give a lot more credence to this answer).
'arrive' becomes 'come' (coming is a kind of arriving).
'with' is a charade indicator (letters next to each other).
'enclosures' becomes 'pens' (pen is a kind of enclosure).
'inside' is an insertion indicator.
're'+'come'='recome'
'recome' enclosing 'pens' is 'RECOMPENSE'.
'about' acts as a link.
Can you help me to learn more?
(Other definitions for recompense that I've seen before include "Compensation" , "Reward for effort or work" , "Amends" , "Payment (for service rendered)" .)