Dance introduces dated pieces that need arranging? (6)
I believe the answer is:
jigsaw
'pieces that need arranging?' is the definition.
(jigsaw pieces must be put together)
'dance introduces dated' is the wordplay.
'dance' becomes 'jig' (jigging is a kind of dancing).
'introduces' is a charade indicator (letters next to each other).
'dated' becomes 'saw' (see can mean to date romantically).
'jig'+'saw'='JIGSAW'
(Other definitions for jigsaw that I've seen before include "Problem with fitting in" , "Puzzle in which pieces must be reassembled" , "Sharp tool (for cutting puzzle into pieces?)" , "Puzzle - powered cutter" , "Picture in pieces" .)