Betting rings to stay (4)
I believe the answer is:
stop
'stay' is the definition.
(I know that stay can be written as stop)
'betting rings to' is the wordplay.
'betting' becomes 'sp'.
'rings' means one lot of letters goes inside another (some letters are ringed or contained by others).
'sp' enclosing 'to' is 'STOP'.
(Other definitions for stop that I've seen before include "Discontinue (an action)" , "Standstill" , "Stay" , "Withhold large amount raised" , "period in US" .)