Chilled response about source of unusual accent (4)
I believe the answer is:
burr
'accent' is the definition.
(I've seen this before)
'chilled response about source of unusual' is the wordplay.
'chilled response' becomes 'brr' (I am not sure about this - if you are sure you should believe this answer much more).
'about' is an insertion indicator.
'source of' says to take the initial letters (the start - or source - of the word).
The first letter of 'unusual' is 'u'.
'brr' enclosing 'u' is 'BURR'.
Can you help me to learn more?
(Other definitions for burr that I've seen before include "Soft regional accent" , "manner of speaking)" , "Prickly seed case that clings to clothing" , "Seed carrying pod with hooks" , "Sticky seed pod" .)