Gambling business infiltrated by hot new exploit (4,2,2)
I believe the answer is:
cash in on
'exploit' is the definition.
(I've seen this before)
'gambling business infiltrated by hot new' is the wordplay.
'gambling business' becomes 'casino' (I can't justify this - if you can you should give a lot more credence to this answer).
'infiltrated by' means one lot of letters goes inside another.
'hot' becomes 'h' (abbreviation eg on taps).
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'casino' placed around 'h' is 'cashino'.
'cashino'+'n'='CASH IN ON'
Can you help me to learn more?
(Other definitions for cash in on that I've seen before include "Turn to one's advantage - no cheques!" , "Make profit from, turn to one's advantage" , "Make large profit or turn to advantage" , "Exploit" .)