Hear bet is off and get some air (7)
I believe the answer is:
breathe
'some air' is the definition.
(thesaurus)
'hear bet is off' is the wordplay.
'is off' is an anagram indicator.
'hear'+'bet'='hearbet'
'hearbet' anagrammed gives 'BREATHE'.
'and get' acts as a link.
(Other definitions for breathe that I've seen before include "Inhale and exhale" , "Inspire and expire air" , "Tell" , "Express" , "eg Inhale" .)