Star's key broadcast (6)
I believe the answer is:
altair
'star's' is the definition.
(Altair is a star in the constellation of Aquila)
'key broadcast' is the wordplay.
'key' becomes 'alt' (the Alt keyboard button).
'broadcast' becomes 'air' (to air on TV).
'alt'+'air'='ALTAIR'
(Other definitions for altair that I've seen before include "A trial (anag) - star" , "Lariat (anag) - star in Aquila" , "Bright star; lariat (anag.)" , "Heavenly body" , "Member of Eagle family" .)