Become brown before ballroom dance (5)
I believe the answer is:
tango
'ballroom dance' is the definition.
(tango is a kind of ballroom dance)
'become brown before' is the wordplay.
'become' becomes 'go' ('go' can be a synonym of 'become').
'brown' becomes 'tan' (tan is a kind of brown).
'before' is a charade indicator (letters next to each other).
'go' after 'tan' is 'TANGO'.
(Other definitions for tango that I've seen before include "Dance originally from Buenos Aires" , "Colourful dance from Argentina" , "Dance; T (radio comms.)" , "Tonga (anag.)" , "Dramatic dance form Argentina" .)