Italian soldiers carrying ammunition, originally stowed away in vessel (6)
I believe the answer is:
tuscan
'italian' is the definition.
(someone from Tuscany in Italy)
'soldiers carrying ammunition originally stowed away in vessel' is the wordplay.
'originally' suggests taking the first letters.
'stowed away in' is an insertion indicator.
'vessel' becomes 'tun' (tun is a kind of vessel).
The initial letters of 'soldiers carrying ammunition' is 'sca'.
'sca' going inside 'tun' is 'TUSCAN'.
(Other definitions for tuscan that I've seen before include "Of region around Florence" , "Person from Siena" , "Classical architecture" , "Relating to a region of Italy" , "From a region of west central Italy" .)