Bet it's neat rum! (4)
I believe the answer is:
ante
'bet' is the definition.
(ante is a kind of bet)
'neat rum' is the wordplay.
'rum' indicates an anagram (rum can mean strange or unusual).
'neat' anagrammed gives 'ANTE'.
'it's' acts as a link.
(Other definitions for ante that I've seen before include "Betting stake" , "Advance stake" , "Prefix meaning before" , "expected from stake" , "not post" .)