Reportedly owing to moisture (3)
I believe the answer is:
dew
'moisture' is the definition.
(I have seen 'Overnight moisture ' mean 'dew' so perhaps 'moisture' could also mean 'dew')
'reportedly owing' is the wordplay.
'reportedly' shows a homophone (sound like).
'owing' becomes 'due' ('due' can be similar in meaning to 'owing').
'due' is a homophone of 'DEW'.
'to' acts as a link.
(Other definitions for dew that I've seen before include "Condensation during the night" , "Night fall of moisture" , "Moisture on ground" , "Dawn deposit" , "Night-time condensate" .)