Coming out of British army corps upset chap (8)
I believe the answer is:
emergent
'coming out of british' is the definition.
'emergent' can be an answer for 'coming' (coming can mean emerging or arriving). I'm not certain of the 'out of british' bit.
'army corps upset chap' is the wordplay.
'army corps' becomes 'reme' (Royal Electrical Mechanical Engineers).
'upset' shows that the letters should be reversed in order.
'chap' becomes 'gent' (both can mean a man).
'reme' in reverse letter order is 'emer'.
'emer'+'gent'='EMERGENT'
Can you help me to learn more?
(Other definitions for emergent that I've seen before include "making an appearance" , "Suddenly appearing" , "Newly independent" , "Rising" , "Coming into existence" .)