Unlikely to chill, no brief garment (9)
I believe the answer is:
loincloth
'brief garment' is the definition.
'loincloth' can be an answer for 'garment' (loincloth is a kind of garment). I'm unsure of the 'brief' bit.
'unlikely to chill no' is the wordplay.
'unlikely' indicates anagramming the letters (an unlikely spelling of the letters).
'to'+'chill'+'no'='tochillno'
'tochillno' anagrammed gives 'LOINCLOTH'.
Can you help me to learn more?
(Other definitions for loincloth that I've seen before include "Minimal garment" , "Simple garment" , "Sort of dhoti" , "Garment Indian may have" , "scanty garment" .)