Maybe too powdery on the surface (10)
I believe the answer is:
overground
'maybe too powdery' is the definition.
I can't judge whether this definition defines the answer.
'on the surface' is the wordplay.
'on' becomes 'over' (over can mean on top of).
'the surface' becomes 'ground' (ground is a kind of surface).
'over'+'ground'='OVERGROUND'
Can you help me to learn more?
(Other definitions for overground that I've seen before include "On the surface" , "a description of very powdery coffee?" .)