I am, alas, returning sausage (6)
I believe the answer is:
salami
'sausage' is the definition.
(salami is a kind of sausage)
'i am alas returning' is the wordplay.
'i am' becomes 'I'm' (contraction).
'returning' is a reversal indicator.
'im'+'alas'='imalas'
'imalas' written backwards gives 'SALAMI'.
(Other definitions for salami that I've seen before include "Sausage served sliced" , "Highly spiced sausage" , "Cured meat" , "Savoury snack" , "Hooked" .)