Ground is to alter betting system (9)
I believe the answer is:
totaliser
'betting system' is the definition.
(I've seen this before)
'ground is to alter' is the wordplay.
'ground' is an anagram indicator ('grind' the letters into a new form).
'is'+'to'+'alter'='istoalter'
'istoalter' with letters rearranged gives 'TOTALISER'.
(Other definitions for totaliser that I've seen before include "Risky system" , "Betting system" , "system for the better" , "Summer" , "you can bet on it!" .)