Disney and an unknown dance as a couple (5)
I believe the answer is:
waltz
'dance as a couple' is the definition.
(a waltz is a dance for two)
'disney and an unknown' is the wordplay.
'disney' becomes 'Walt' (Walt Disney).
'and' says to put letters next to each other.
'an unknown' becomes 'z' (algebra).
'walt'+'z'='WALTZ'
(Other definitions for waltz that I've seen before include "Last dance?" , "Ballroom dance, originally from Germany" , "Dance in three-four time" , "German dance" , "Three-time dance" .)