Pasta ration in mess, about one gram (8)
I believe the answer is:
rigatoni
'pasta' is the definition.
(rigatoni is a kind of pasta)
'ration in mess about one gram' is the wordplay.
'in mess' indicates anagramming the letters.
'about' is an insertion indicator.
'one' becomes 'i' (Roman numeral).
'gram' becomes 'g' ('g' can be a synonym of 'gram').
'ration' is an anagram of 'ratoni'.
'i'+'g'='ig'
'ratoni' enclosing 'ig' is 'RIGATONI'.
(Other definitions for rigatoni that I've seen before include "Type of pasta" , "Pasta dish" , "Short fluted tubes of pasta" , "Pasta - I got rain (anag)" , "Foodstuff" .)