Old lady extremely cold in buff (7)
I believe the answer is:
nankeen
'buff' is the definition.
(nankeen can mean a buff or beige colour)
'old lady extremely cold' is the wordplay.
'old lady' becomes 'nan' (British slang for grandmother).
'extremely cold' becomes 'keen' (similar in meaning. I am not sure about the 'extremely' bit.).
'nan'+'keen'='NANKEEN'
'in' acts as a link.
Can you help me to learn more?
(Other definitions for nankeen that I've seen before include "mustard colour" , "Buff colour" , "Yellowish stuff" , "trouser material" , "Buff-coloured cotton fabric" .)