A record in polo games (3)
I believe the answer is:
log
'a record' is the definition.
(I know that log is a more specific form of the action record)
'in polo games' is the wordplay.
'in' says the answer is hidden in the clue.
'LOG' is hidden in the letters of 'polo games'.
(Other definitions for log that I've seen before include "fuel consumed" , "Official record of events" , "Written account of a voyage" , "Diary kept by ship's captain" , "Record kept" .)