Heavenly body and compiler in bed! (5)
I believe the answer is:
comet
'heavenly body' is the definition.
(comet is a kind of heavenly body)
'compiler in bed' is the wordplay.
'compiler' becomes 'me' (the person who is writing these clues).
'in' indicates putting letters inside.
'bed' becomes 'cot' (cot is a kind of bed).
'me' going within 'cot' is 'COMET'.
'and' acts as a link.
(Other definitions for comet that I've seen before include "Early jetliner" , "Small extraterrestrial body" , "Celestial orbiter" , "Shooting star" , "Halley's phenomenon in space" .)