Seed finally winning serves taking new balls (6)
I believe the answer is:
Here is my best explanation:
'balls' is the definition.
(I've seen this before)
'seed finally winning serves taking new' is the subsidiary indication.
'finally' indicates one should 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' going around 'n' is 'ances'.
(Other definitions for dances that I've seen before include "Eg, tango and samba", "Ascend (anag)", "Moves to music", "Trips the light fantastic", "Set movements to music", "Waltzes", "Can-can, cha-cha etc", "Jigs", "Eg, waltzes, tangos, etc" and "Balls".)