Reward left buried in concrete (8)
I believe the answer is:
requital
'reward' is the definition.
(I've seen this before)
'left buried in concrete' is the wordplay.
'left' becomes 'quit' (I've seen this in other clues).
'buried in' indicates putting letters inside (inserted letters get buried).
'concrete' becomes 'real' (associated in meaning).
'quit' placed into 'real' is 'REQUITAL'.
(Other definitions for requital that I've seen before include "Revenge - quartile (anag)" , "Satisfactory compensation" , "Amends" , "Payment in return" , "Recompense" .)