Heavy metal band's flamboyant front man (7)
I believe the answer is:
mercury
This clue is a double definition.
'heavy metal' is the first definition.
(mercury is a heavy metal)
'band's flamboyant front man' is the second definition.
(Queen frontman Freddie Mercury)
(Other definitions for mercury that I've seen before include "Planet - liquid metal" , "Planet nearest the sun" , "First planet from the Sun" , "Planet next to the sun" , "Messenger of the Gods, or a chemical element" .)