Some mediocre grub ma has picked up? (9)
I believe the answer is:
hamburger
'some mediocre grub ma has picked up?' is the definition.
I can't tell whether this definition defines the answer.
'some mediocre grub ma has picked up?' is the wordplay.
'some' says the answer is hidden in the clue (some parts of the word are used).
'up?' says the letters should be written in reverse (in down clue: letters go upwards).
'regrubmah' is hidden in the letters of 'mediocre grub ma has picked'.
'regrubmah' written backwards gives 'HAMBURGER'.
Can you help me to learn more?
(Other definitions for hamburger that I've seen before include "Staple of the fast food industry" , "Beef dish from German city" , "beefcake" , "minced beef roll" , "Fast-food item" .)