Bound to make a sound bet (6)
I believe the answer is:
gambol
'bound' is the definition.
(thesaurus)
'a sound bet' is the wordplay.
'a sound' shows a homophone (sound like).
'bet' becomes 'gamble' (I've seen this before).
'gamble' is a homophone of 'GAMBOL'.
'to make' acts as a link.
(Other definitions for gambol that I've seen before include "Frisk about and bet, by the sound of it" , "Dance" , "Spring" , "Skip" , "jump for joy" .)