High and dry area reduced to dust (7)
I believe the answer is:
aground
'high and dry' is the definition.
(I've seen this before)
'area reduced to dust' is the wordplay.
'area' becomes 'a' (maths abbreviation).
'reduced to dust' becomes 'ground' (I've seen this before).
'a'+'ground'='AGROUND'
(Other definitions for aground that I've seen before include "Unable to move" , "(Ship) unable to float" , "on the bed" , "(Of a ship) stuck on the seabed" , "(Of ship) touching the bottom" .)