Macaroni perhaps in soup, a starter (5)
I believe the answer is:
pasta
'macaroni perhaps' is the definition.
(macaroni is a kind of pasta)
'in soup a starter' is the wordplay.
'in' indicates a hidden word.
'PASTA' is hidden within 'soup a starter'.
(Other definitions for pasta that I've seen before include "Eg, tagliatelle" , "Spaghetti, perhaps" , "Staple Italian food base" , "Italian dough" , "Macaroni, for example" .)