Mention betting each thousand (5)
I believe the answer is:
speak
'mention' is the definition.
(thesaurus)
'betting each thousand' is the wordplay.
'betting' becomes 'sp'.
'each' becomes 'ea' (abbreviation).
'thousand' becomes 'k' (synonyms).
'sp'+'ea'+'k'='SPEAK'
(Other definitions for speak that I've seen before include "Say something" , "give a lecture" , "express" , "Talk" , "Converse" .)