Clue: … this perhaps, showing head's a 6 (5,4)
Answer: BOSSA NOVA
Explanation: Definition: … this perhaps
 BOSS(head/chief) **plus**(…'s /has) A + NOVA(a star/answer to 6 across, that, for a while, becomes brighter and then fades back)
Defn: Continuing from the previous clue, "dancing this, perhaps", ie. an example of a dance, from Brazil, in this case.
Channeling Austin Powers: