Regrettably sent back motorway food (6)
I believe the answer is:
salami
'food' is the definition.
(salami is a kind of food)
'regrettably sent back motorway' is the wordplay.
'regrettably' becomes 'alas' ('alas' is said before regrettable information).
'sent back' says the letters should be written in reverse.
'motorway' becomes 'MI' (resembles M1, English motorway).
'alas' back-to-front is 'sala'.
'sala'+'mi'='SALAMI'
(Other definitions for salami that I've seen before include "Spicy preserved sausage" , "Strongly flavoured Italian sausage" , "Highly-seasonal sausage" , "One kind of tactics" , "Garlic- flavoured sausage" .)