Punch sportsman's partner for chatting (7)
I believe the answer is:
chinwag
'partner for chatting' is the definition.
I can't tell whether this defines the answer.
'punch sportsman's' is the wordplay.
'punch' becomes 'chin' (slang term meaning to punch someone on the chin).
'sportsman's' becomes 'wag' (I can't explain this - if you can you should believe this answer much more).
'chin'+'wag'='CHINWAG'
Can you help me to learn more?
(Other definitions for chinwag that I've seen before include "Informal conversation" , "Informal chat moving lower jaw" , "rabbit" , "Natter" , "Chat (slang)" .)