Ten-sided figure (7)
I believe the answer is:
decagon
'ten-sided figure' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for decagon that I've seen before include "10-sided figure" , "Plane shape" , "Ten-sided shape" , "Go, dance on geometric figure with ten sides" , "A polygon -- eg can-do (anag)" .)