Heavenly body ran into Earth before first two in orbit (6)
I believe the answer is:
meteor
'heavenly body' is the definition.
(meteor is a kind of heavenly body)
'ran into earth before first two in orbit' is the wordplay.
'ran into' becomes 'met'.
'earth' becomes 'e'.
'before first two in orbit' becomes 'or' (I can't justify this - if you can you should give a lot more credence to this answer).
'met'+'e'+'or'='METEOR'
(Other definitions for meteor that I've seen before include "Remote (anag)" , "Glowing heavenly body" , "Small piece of matter in the solar system" , "Shooting star" , "Remote sort of heavenly body" .)