He put neat rum in to increase risk (2,3,4)
I believe the answer is:
up the ante
'to increase risk' is the definition.
(poker)
'he put neat rum' is the wordplay.
'rum' is an anagram indicator (rum can mean strange or unusual).
'he'+'put'+'neat'='heputneat'
'heputneat' with letters rearranged gives 'UP THE ANTE'.
'in' acts as a link.
(Other definitions for up the ante that I've seen before include "Pet tuna he used to raise poker stakes" , "Increase the stakes" , "Increase what is at stake" , "Lift stakes" , "Demand more" .)