Italian dish in Dad's Army? (5)
I believe the answer is:
pasta
'italian dish' is the definition.
(I've seen this before)
'dad's army?' is the wordplay.
'dad's' becomes 'pa's' ('pa' can be a synonym of 'dad').
'army?' becomes 'TA' (abbreviation for Territorial Army).
'pas'+'ta'='PASTA'
'in' acts as a link.
(Other definitions for pasta that I've seen before include "Dried flour paste for making Italian food" , "Italian dough" , "Eg, tagliatelle" , "shells, perhaps" , "Spaghetti, ziti, fusilli, for example" .)