Vessel with top shot, a nostrum (7)
I believe the answer is:
panacea
'nostrum' is the definition.
(synonyms)
'vessel with top shot a' is the wordplay.
'vessel' becomes 'pan' (vessel or container for cooking).
'with' is a charade indicator (letters next to each other).
'top shot' becomes 'ace' (I've seen this in another clue).
'pan'+'ace'+'a'='PANACEA'
(Other definitions for panacea that I've seen before include "Universal medicine" , "A cure-all for diseases or troubles" , "that can make anything better" , "Cure for all ills" , "Nostrum" .)