It's due to be pronounced wet (3)
I believe the answer is:
dew
'wet' is the definition.
(moisture on the ground)
'it's due to be pronounced' is the wordplay.
'to be pronounced' indicates a 'sounds like' (homophone) clue.
'due' sounds like 'DEW'.
(Other definitions for dew that I've seen before include "Night-time condensation" , "Morning or evening condensation" , "Small drops of moisture" , "Moisture on grass" , "Moisture deposited overnight" .)