Current shade up during day (6)
I believe the answer is:
modern
'current' is the definition.
('modern' is associated in meaning with 'current')
'shade up during day' is the wordplay.
'shade' becomes 'red'.
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'during' is an insertion indicator.
'day' becomes 'mon'.
'red' reversed gives 'der'.
'der' put within 'mon' is 'MODERN'.
(Other definitions for modern that I've seen before include "Activity of 18 ac" , "Up to date, of present times" , "The very latest available" , "See 11" , "Novel" .)