Dance Armstrong was first to do? (8)
I believe the answer is:
moonwalk
I believe this is a double definition.
'dance' is the first definition.
(I know that moonwalk is a type of dance)
'armstrong was first to do?' is the second definition.
(Neil Armstrong walked on the Moon)
(Other definitions for moonwalk that I've seen before include "Dance as if in low gravity" , "Jackson's dance - Armstrong's first" , "Dance performed by Michael Jackson" , "Lunar stroll - disco manoeuvre" , "Dance imitating astronauts" .)