Grandma eager for material (7)
I believe the answer is:
nankeen
'for material' is the definition.
(nankeen is a type of material)
'grandma eager' is the wordplay.
'grandma' becomes 'nan' (nan can informally mean a grandmother).
'eager' becomes 'keen' (I've seen this before).
'nan'+'keen'='NANKEEN'
(Other definitions for nankeen that I've seen before include "Yellowish stuff" , "Chinese cotton cloth" , "Buff-coloured cotton fabric" , "Buff colour(ed cloth)" , "hard-wearing stuff" .)