Latin American ballroom dance (5)
(Other definitions for rumba that I've seen before include "South American dance" , "Ballroom dance of Cuban origin" , "Caribbean dance" , "Cuban folk dance" , "Cuban folk-dance" .)
(Other definitions for tango that I've seen before include "Dance originally from Buenos Aires" , "Activity requiring two to" , "tee" , "one followed by uniform" , "reputedly takes two" .)
'latin american ballroom dance' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for cha-cha that I've seen before include "certain steps" , "Latin American ballroom dance" , "Latin-American dance" , "Modern ballroom dance from Latin America" , "Repetitive Latin American dance" .)