It doesn't describe the present schoolboy (6)
I believe the answer is:
truant
This clue might be a double definition.
'it doesn't describe' is the first definition.
The definition suggests a singular noun which matches the answer.
'the present schoolboy' is the second definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
Can you help me to learn more?
(Other definitions for truant that I've seen before include "Pupil who stays away from school with permission" , "Someone playing hookey from school" , "Inexcusably absent" , "Delinquent" , "'Bunk off'" .)