Discard back to front gambling game (5)
I believe the answer is:
scrap
'discard back' is the definition.
'scrap' can be an answer for 'discard' (scrapping is a kind of discarding). I'm not certain of the 'back' bit.
'front gambling game' is the wordplay.
'front gambling' becomes 's' (I can't justify this - if you can you should give a lot more credence to this answer).
'game' becomes 'crap game' (crap game is a kind of game).
's'+'crap'='SCRAP'
'to' is the link.
Can you help me to learn more?
(Other definitions for scrap that I've seen before include "Fragment or slang fight (5)" , "A little bit of a fight" , "Axe" , "Scuffle" , "Small piece - fight" .)