Dance understood to be a puzzle (6)
I believe the answer is:
jigsaw
'a puzzle' is the definition.
(jigsaw puzzle is a kind of puzzle)
'dance understood' is the wordplay.
'dance' becomes 'jig' (jig is a kind of dance**).
'understood' becomes 'saw' ('see' can be a synonym of 'understand').
'jig'+'saw'='JIGSAW'
'to be' is the link.
(Other definitions for jigsaw that I've seen before include "Sharp tool (for cutting puzzle into pieces?)" , "Type of puzzle" , "Problem with fitting in" , "As pastime" , "Puzzle fittingly completed" .)