Deserts are sandy (7)
I believe the answer is:
strands
'deserts' is the definition.
(stranding is a kind of deserting)
'are sandy' is the wordplay.
I cannot quite see how this works, but
'are' could be 'ran' (running is a kind of being) and 'ran' is located in the answer.
The remaining letters 'stds' is a valid word which might be clued in a way I don't see.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for strands that I've seen before include "Threads or beaches" , "Leaves helpless on the sand" , "Filaments" , "Maroons" , "Threads, fibres" .)