Confusing thing, darkness (5)
I believe the answer is:
night
'darkness' is the definition.
(night is a kind of darkness)
'confusing thing' is the wordplay.
'confusing' indicates anagramming the letters.
'thing' with letters rearranged gives 'NIGHT'.
(Other definitions for night that I've seen before include "Hours of darkness" , "Tennyson's "black bat"" , "''Twas the ... before Christmas, when all through the house / Not a creature was stirring, not even a mouse''" , "Time for bed" , "Ignorance" .)