Extremely long sort of year! (5)
I believe the answer is:
light
This clue might be a double definition.
'extremely long sort' is the first definition.
The definition and answer can be both human attributes as well as being singular nouns.
Maybe they are linked in a way I don't understand?
'year' is the second definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'of' is the link.
Can you help me to learn more?
(Other definitions for light that I've seen before include "Radiance" , "not overburdened" , "Not dark; not heavy" , "Mild" , "Illumination - not serious!" .)