Green is seen all the time (6)
I believe the answer is:
common
I believe this clue is a double definition.
'green' is the first definition.
(I know that green can be written as common)
'seen all the time' is the second definition.
(I've seen this in another clue)
'is' acts as a link.
(Other definitions for common that I've seen before include "Ordinary; green space" , "Usual, of no particular distinction" , "Nous" , "Vulgar; not rare" , "Shared - vulgar" .)