First vessel sent back (3)
I believe the answer is:
top
'first' is the definition.
(top can mean the best or first)
'vessel sent back' is the wordplay.
'vessel' becomes 'pot' (type of container).
'sent back' is a reversal indicator.
'pot' written backwards gives 'TOP'.
(Other definitions for top that I've seen before include "Better" , "Highest, child's toy" , "jumper, say?" , "Peak; beat" , "Summit or spinning toy" .)