His game is unremunerative (3)
I believe the answer is:
mug
'his game' is the definition.
'mug' can be an answer for 'game' (thesaurus). I'm not sure about the 'his' bit.
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for mug that I've seen before include "concentrate on studying" , "person's face" , "Fool - face - vessel" , "Slangy victim, by gum" , "Large cup without a saucer" .)