Go and dance madly in a ten-sided figure (7)
I believe the answer is:
decagon
'a ten-sided figure' is the definition.
(I've seen this before)
'go and dance madly' is the wordplay.
'and' says to put letters next to each other.
'madly' indicates an anagram.
'go' after 'dance' is 'dancego'.
'dancego' with letters rearranged gives 'DECAGON'.
'in' acts as a link.
(Other definitions for decagon that I've seen before include "Figure with 10 sides" , "Go, dance on geometric figure with ten sides" , "A polygon -- eg can-do (anag)" , "Ten-sided shape" , "10-sided figure" .)