Celestial body with a tail (5)
I believe the answer is:
comet
'celestial body with a tail' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for comet that I've seen before include "body found in space" , "Rudolph's companion" , "Plane" , "Celestial orbiter" , "Dancer's colleague" .)