Dublin money once used for gamble (4)
I believe the answer is:
punt
This clue is a double definition.
'dublin money once' is the first definition.
(pre-Euro currency of Ireland)
'for gamble' is the second definition.
(to take a punt is to gamble)
'used' is the link.
(Other definitions for punt that I've seen before include "Pole-propelled boat" , "Flat-bottomed boat propelled by pole" , "Boat; Irish ex-currency" , "Stake" , "Riverboat" .)