Threat posed by introduction of Calor gas (7)
I believe the answer is:
chatter
'gas' is the definition.
(thesaurus)
'threat posed by introduction of calor' is the wordplay.
'posed' indicates anagramming the letters (I've seen 'pose' mean this (the letters must be re-posed into a new order)).
'by' says to put letters next to each other.
'introduction of' suggests taking the first letters.
The initial letter of 'calor' is 'c'.
'threat' is an anagram of 'hatter'.
'hatter' after 'c' is 'CHATTER'.
(Other definitions for chatter that I've seen before include "Gas" , "Trivial conversation" , "Speak rapidly and incessantly" , "Idle gossip" , "Talk incessantly" .)