Pork producer making a sandwich of Old Trafford's Walls sausage (3,3)
I believe the answer is:
hot dog
'sausage' is the definition.
(thesaurus)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for hot dog that I've seen before include "Sausage in bread-roll for thermal canine" , "Sausage in breae roll" , "Sausage snack" , "Sausage in a bun" , "Sausage sandwich - acrobatic skier" .)