Cleaner sold in green canisters (5)
I believe the answer is:
comet
'cleaner sold in green canisters' 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 "Heavenly body with a fiery tail" , "Long distance traveller" , "potential space invader" , "bright star" , "Small extraterrestrial body" .)