Deer on extraterrestrial vessel (6)
I believe the answer is:
bucket
'vessel' is the definition.
(I know that bucket is a type of vessel)
'deer on extraterrestrial' is the wordplay.
'deer' becomes 'buck' (male deer).
'on' is a charade indicator (letters next to each other).
'extraterrestrial' becomes 'et' (I've seen this in other clues).
'buck'+'et'='BUCKET'
(Other definitions for bucket that I've seen before include "Resembling soil" , "Part of waterwheel" , "Waterwheel compartment" , "Carrier for liquids" , "Round open water container with handle" .)