The prize is back in a back sliding compartment (6)
I believe the answer is:
reward
'the prize' is the definition.
(a prize may be given as a reward)
'back sliding compartment' is the wordplay.
'back' says the letters should be written in reverse.
'sliding compartment' becomes 'drawer' (I've seen this before).
'drawer' back-to-front is 'REWARD'.
'is back in a' is the link.
This may not be correct. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for reward that I've seen before include "Reinforcement for good behaviour" , "Present given to mark service or good deed" , "Bounty for, eg, capturing outlaw" , "Compensation for a good deed" , "Deserts" .)