Polo game division (6)
I believe the answer is:
chukka
'polo game division' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for chukka that I've seen before include "Polo game division" , "Division of a polo match" , "period of game" , "7 1/2 minutes of polo" , "A period of play in horse polo" .)