Dance essential to aged is conga (5)
I believe the answer is:
disco
'dance' is the definition.
(disco can mean a dance event)
'essential to aged is conga' is the wordplay.
'essential to' indicates a hidden word (letters in the inside or essence of the clue).
'DISCO' is hidden in the letters of 'aged is conga'.
(Other definitions for disco that I've seen before include "party for dancers" , "Dance hall - music by Donna Summer and the Bee Gees, say" , "music supplier" , "Doc is dancing here" , "Style of music/dancing" .)