Old lady, impatient, possibly in buff (7)
I believe the answer is:
nankeen
'buff' is the definition.
(nankeen can mean a buff or beige colour)
'old lady impatient' is the wordplay.
'old lady' becomes 'nan' (British slang for grandmother).
'impatient' becomes 'keen' (keen can mean eager or impatient).
'nan'+'keen'='NANKEEN'
'possibly in' acts as a link.
(Other definitions for nankeen that I've seen before include "Hard-wearing fabric, originally from China" , "hard-wearing stuff" , "Yellowish cotton cloth" , "mustard colour" , "Buff colour(ed cloth)" .)