Bank concede old exit charges (8)
I believe the answer is:
gradient
'bank' is the definition.
(both can mean sloped ground)
'concede old exit charges' is the wordplay.
'concede' becomes 'grant' (synonyms).
'old exit' becomes 'die' (synonyms. I am not sure about the 'old' bit.).
'charges' means one lot of letters goes inside another (charge can mean to charge into something).
'grant' enclosing 'die' is 'GRADIENT'.
Can you help me to learn more?
(Other definitions for gradient that I've seen before include "Perhaps one in ten" , "Treading (anag) - slope" , "Bank" , "Third OT book" , "Degree of slope in a road" .)