The Greek god rested on a maybe Grecian vessel (6)
I believe the answer is:
saturn
'the greek god' is the definition.
'saturn' can be an answer for 'god' (Saturn is an example). I'm unsure of the 'the greek' bit.
'rested on a maybe grecian vessel' is the wordplay.
I cannot quite see how this works, but
'rested' could be 'sat' (to sit is to rest) and 'sat' is found within the answer.
'vessel' could be 'urn' (urn is a kind of vessel) and 'urn' is found in the answer.
No letters remain.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for saturn that I've seen before include "One of the 1 across" , "orbits the sun" , "The dark planet" , "Giant planet" , "Roman god - gas giant" .)