Exceptional power - a lot is needed for this game (5,4)
I believe the answer is:
water polo
'this game' is the definition.
(water polo is a kind of game)
'exceptional power a lot is needed' is the wordplay.
'exceptional' is an anagram indicator (an unusual or exceptional ordering of the letters).
'is needed' says to put letters next to each other.
'power'+'a'+'lot'='poweralot'
'poweralot' with letters rearranged gives 'WATER-POLO'.
'for' acts as a link.
(Other definitions for water polo that I've seen before include "Team sport played in a swimming pool" , "event" , "Game played by tams of swimmers with large ball (5.4)" , "Seven-a-side game involving swimming" , "Sport for swimmers" .)