Lean back into serve for gritty and absorbing stuff (3,6)
I believe the answer is:
cat litter
'gritty and absorbing stuff' is the definition.
'lean back into serve' is the wordplay.
'lean' becomes 'tilt' (synonyms).
'back' says the letters should be written backwards.
'into' indicates putting letters inside.
'serve' becomes 'cater' (I can't justify this - if you can you should believe this answer much more).
'tilt' backwards is 'tlit'.
'tlit' put into 'cater' is 'CAT LITTER'.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for cat litter that I've seen before include "Absorbent material for feline waste" , "Contents of pussy's tray" , "Absorbent material in pet's basket" , "dropping in here?" .)