Darkness close: closer in east (5)
I believe the answer is:
night
'darkness' is the definition.
(night is a period of darkness)
'close closer in east' is the wordplay.
'close' becomes 'nigh' (similar in meaning).
'closer in' says to take the final letters (I've seen 'close in' mean this).
The last letter of 'east' is 't'.
'nigh'+'t'='NIGHT'
(Other definitions for night that I've seen before include "Dark hours" , "A Hard Day's (the Beatles)" , "Evening" , "- School, - owl" , "End of the day" .)