A Gran worked with old wool (6)
I believe the answer is:
angora
'wool' is the definition.
(thesaurus)
'a gran worked with old' is the wordplay.
'worked with' indicates anagramming the letters.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'gran' mixed up with 'o' gives 'ngora'.
'a'+'ngora'='ANGORA'
(Other definitions for angora that I've seen before include "Soft yarn from goat" , "Wool from hair of goats" , "Soft yarn from certain goats" , "Yarn or fabric from hair of goats or rabbits" , "Name of goat yielding 10 across" .)