Attributable to moisture, we hear (3)
I believe the answer is:
due
'attributable' is the definition.
(thesaurus)
'moisture we hear' is the wordplay.
'moisture' becomes 'dew' (I have seen 'Overnight moisture ' mean 'dew' so perhaps 'moisture' could also mean 'dew').
'we hear' indicates a 'sounds like' (homophone) clue.
'dew' sounds like 'DUE'.
'to' acts as a link.
(Other definitions for due that I've seen before include "Expected at any moment" , "Owed as a debt" , "Ripe for payment or arrival" , "Escort" , "Requisite" .)