Could this make sandstone be firm? (5,4,6)
I believe the answer is:
stand ones ground
'could' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.
'make sandstone be firm?' is the wordplay.
I cannot really see how this works, but
'make' could be 'ground' (grounding is a kind of making) and 'ground' is found within the answer.
an anagram of 'sandstone' is 'standones' which is present in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
'this' acts as a link.
Can you help me to learn more?
(Other definitions for stand ones ground that I've seen before include "Maintain personal position" , "Refuse to move" .)