Fast food grub her ma cooked (9)
I believe the answer is:
hamburger
'fast food' is the definition.
(I've seen this before)
'grub her ma cooked' is the wordplay.
'cooked' indicates anagramming the letters (letters cooked into a new form).
'grub'+'her'+'ma'='grubherma'
'grubherma' with letters rearranged gives 'HAMBURGER'.
(Other definitions for hamburger that I've seen before include "Item of fast food" , "minced beef roll" , "Citizen of Europe" , "Fried cake of minced beef served on a bun" , "beefcake" .)