Dad's Army food (5)
I believe the answer is:
pasta
'food' is the definition.
(pasta is a kind of food)
'dad's army' is the wordplay.
'dad's' becomes 'pas' ('pa' can be a synonym of 'dad').
'army' becomes 'ta' (abbreviation for Territorial Army).
'pas'+'ta'='PASTA'
(Other definitions for pasta that I've seen before include "dish from Italy" , "Tagliatelle, for example" , "Fusilli, conchiglie and penne" , "Spaghetti, ziti, fusilli, for example" , "Fusilli, tortelloni etc" .)