Top score in playing pontoon or Newmarket for starters (5)
I believe the answer is:
ippon
'top score' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.
'in playing pontoon or newmarket for starters' is the wordplay.
'for starters' indicates taking the first letters.
The first letters of 'in playing pontoon or newmarket' is 'IPPON'.
Can you help me to learn more?
(Other definitions for ippon that I've seen before include "winning point for technique" , "winning score" .)