Some insulting letters going into fire (5)
I believe the answer is:
ingle
'fire' is the definition.
(thesaurus)
'some insulting letters going' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'INGLE' can be found hidden inside 'insulting letters going'.
'into' acts as a link.
(Other definitions for ingle that I've seen before include "potentially hot situation" , "Domestic fireplace" , "Dizziness from imbalance" , "Fireplace in a room" , "warm part of house" .)