Humid days came to an end (6)
I believe the answer is:
closed
'came to an end' is the definition.
(close can mean to come to an end or finish)
'humid days' is the wordplay.
'humid' becomes 'close' (I've seen this before).
'days' becomes 'd'.
'close'+'d'='CLOSED'
(Other definitions for closed that I've seen before include "Held in private" , "clinched the sale" , "See 1" , "Shut" , "Not longer open" .)