Resistant to cooking hotpot, mostly, and fare that’s stewed (9)

'resistant to cooking' is the definition.
I can't tell whether this definition defines the answer.

'hotpot mostly and fare that's stewed' is the wordplay.
'mostly' means to remove the last letter (most but not all of the word).
'and' says to put letters next to each other.
'that's stewed' is an anagram indicator.
'hotpot' with its last letter taken away is 'hotpo'.
'hotpo' put after 'fare' is 'farehotpo'.
'farehotpo' is an anagram of 'HEATPROOF'.

Can you help me to learn more?