Short battle to save Italian river sport
I believe the answer is:
water polo
'sport' is the definition.
(water polo is a kind of sport)
'short battle to save italian river' is the wordplay.
'short' means to remove the last letter.
'battle' becomes 'waterloo' (Waterloo is an example).
'to save' is an insertion indicator.
'italian river' becomes 'po'.
'waterloo' with its last letter taken away is 'waterlo'.
'waterlo' going around 'po' is 'WATER-POLO'.
(Other definitions for water polo that I've seen before include "Team sport played in a swimming pool" , "Team sport with wet participants" , "Game played by teams of swimmers with large ball" , "event" , "Game played by tams of swimmers with large ball (5.4)" .)