Standard for example aboard vessel (6)
I believe the answer is:
flagon
'vessel' is the definition.
(flagon is a kind of vessel)
'standard for example aboard' is the wordplay.
'standard for example' becomes 'flag' (standard is a kind of flag).
'aboard' becomes 'on'.
'flag'+'on'='FLAGON'
(Other definitions for flagon that I've seen before include "Large vessel with a handle and spout" , "Red or white container" , "Wine jug" , "Large rounded bottle, may contain cider" , "Large bottle for alcohol" .)