So, coming back in, Les made a deposit (5)
I believe the answer is:
loess
'deposit' is the definition.
(sediment deposited by wind)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for loess that I've seen before include "geological feature" , "desposit" , "Compacted wind-blown sediment (geology)" , "Silt deposit" , "Wind-deposited silt" .)