Problem with this Roman vessel (6)
I believe the answer is:
hiccup
'problem' is the definition.
(I've seen this before)
'with this roman vessel' is the wordplay.
'with' is a charade indicator (letters next to each other).
'this roman' becomes 'hic' ('here' in Latin).
'vessel' becomes 'cup' (cup is a type of vessel).
'hic' next to 'cup' is 'HICCUP'.
(Other definitions for hiccup that I've seen before include "Reflex spasm of the diaphragm" , "Involuntary glottal closure" , "Temporary setback (colloq.)" , "Spasm of the diaphragm or an informal hitch" , "Minor setback" .)