He is finally snookered in return (5)
I believe the answer is:
derek
'he' is the definition.
'finally snookered in return' is the wordplay.
'finally' suggests the final letters.
'in return' becomes 'erek' (I can't justify this - if you can you should believe this answer much more).
The final letter of 'snookered' is 'd'.
'd'+'erek'='DEREK'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for derek that I've seen before include "Fellow" , "Man's name" , "- and the Dominos was Eric Clapton's band" , "Sir - - Jacobi (actor)" .)