Seed finally winning serves taking new balls (6)
I believe the answer is:
dances
'balls' is the definition.
(I've seen this before)
'seed finally winning serves taking new' is the wordplay.
'finally' says to take the final letters.
'winning serves' becomes 'aces' (I've seen this before).
'taking' indicates putting letters inside.
'new' becomes 'n'.
The last letter of 'seed' is 'd'.
'aces' enclosing 'n' is 'ances'.
'd'+'ances'='DANCES'
(Other definitions for dances that I've seen before include "Eg, tango and samba" , "Set movements to music" , "Ascend (anag)" , "Moves to music" , "Jigs" .)