100 litres in a round cooking pot (8)
I believe the answer is:
cauldron
'pot' is the definition.
(cauldron is a kind of pot)
'100 litres in a round cooking' is the wordplay.
'100' becomes 'C' (Roman numeral).
'litres' becomes 'l' (abbreviation).
'in' is an insertion indicator.
'cooking' is an anagram indicator (cook can mean to falsify or distort).
'a'+'round'='around'
'around' is an anagram of 'audron'.
'l' inserted within 'audron' is 'auldron'.
'c'+'auldron'='CAULDRON'
(Other definitions for cauldron that I've seen before include "Witches' pot" , "Very large pot used for boiling" , "A large deep pot for boiling things" , "Witches' vessel" , "Place that's seething" .)