Owing, say, to condensation (3)
I believe the answer is:
dew
'condensation' is the definition.
(dew is a kind of condensation)
'owing say' is the wordplay.
'owing' becomes 'due' (similar in meaning).
'say' shows a homophone (sound like).
'due' is a homophone of 'DEW'.
'to' acts as a link.
(Other definitions for dew that I've seen before include "Night-time moisture" , "Night fall of moisture" , "Wed in morning moisture" , "Condensation at beginning or end of day" , "'The foggy, foggy - - ' (song)" .)