Bet on and it's slow (7)
I believe the answer is:
andante
'slow' is the definition.
(similar in meaning)
'bet on and' is the wordplay.
'bet' becomes 'ante' (ante is a kind of bet).
'on' means one lot of letters go next to another.
'ante' put after 'and' is 'ANDANTE'.
'it's' is the link.
(Other definitions for andante that I've seen before include "(Of tempo) moderately slow" , "not quickly" , "deliberately played" , "Moderately slow movement" , "Fairly slow (mus.)" .)