Arguments in favour of Italian down the hatch (6)
I believe the answer is:
prosit
'down the hatch' is the definition.
(both are toasts said before having a drink)
'arguments in favour of italian' is the wordplay.
'arguments in favour of' becomes 'pros'.
'italian' becomes 'it'.
'pros'+'it'='PROSIT'
(Other definitions for prosit that I've seen before include "Good health! Cheers!" , "Good luck to you" , "... [good-health]" , "I sport with a drinking toast in Germany" , "Sir, opt for a toast" .)