Dance leader with a star flaring up (5,4)
I believe the answer is:
bossa nova
'dance' is the definition.
(I've seen this before)
'leader with a star flaring up' is the wordplay.
'leader' becomes 'boss' (boss is a kind of leader).
'with' says to put letters next to each other.
'star flaring up' becomes 'nova' (I've seen this before).
'boss'+'a'+'nova'='BOSSA NOVA'
(Other definitions for bossa nova that I've seen before include "Brazil's measure" , "(Music for) a Brazilian dance" , "Brazilian music, rhythmically related to the samba" , "lively dance" , "Dance from Brazil similar to samba" .)