Alas, I'm upset by Italian sausage (6)
I believe the answer is:
salami
'italian sausage' is the definition.
(I've seen this in another clue)
'alas i'm upset' is the wordplay.
'upset' indicates an anagram.
'alas'+'im'='alasim'
'alasim' with letters rearranged gives 'SALAMI'.
'by' acts as a link.
(Other definitions for salami that I've seen before include "Garlic- flavoured sausage" , "A highly seasoned type of sausage" , "Spiced Italian sausage" , "One kind of tactics" , "Preserved meat sausage" .)