Almost hide rubble (5)
I believe the answer is:
scree
'rubble' is the definition.
(I've seen this in another clue)
'almost hide' is the wordplay.
'almost' means to remove the last letter (most of the word but not all of it).
'hide' becomes 'screen' (I've seen this in another clue).
'screen' with its final letter removed is 'SCREE'.
(Other definitions for scree that I've seen before include "Loose shifting stones" , "bits of rock" , "Rock debris at the base of a cliff" , "Sloping mass of loose rock at the base of a cliff" , "Loose debris on a mountain slope" .)