At the end of the day, close on time (5)
I believe the answer is:
night
'time' is the definition.
(night is a kind of time)
'at the end of the day close on' is the wordplay.
'the end of' says to take the final letters.
'the day close' becomes 'nigh' (I can't justify this - if you can you should believe this answer much more).
'on' is a charade indicator (letters next to each other).
The final letter of 'at' is 't'.
't' put after 'nigh' is 'NIGHT'.
Can you help me to learn more?
(Other definitions for night that I've seen before include "Thing (anag)" , "What proverbially follows day" , "Dark hours" , "Day's partner" , "'She walks in beauty, like the . . . . .' (Byron)" .)