It nourishes teachers introducing old verse books (9)
I believe the answer is:
nutriment
'it nourishes' is the definition.
The definition suggests a singular noun which matches the answer.
'teachers introducing old verse books' is the wordplay.
'teachers' becomes 'nut' (National Union of Teachers).
'introducing' says to put letters next to each other (some letters go before others).
'old verse' becomes 'rime' (archaic spelling of 'rhyme').
'books' becomes 'NT' (New Testament).
'nut'+'rime'+'nt'='NUTRIMENT'
Can you help me to learn more?
(Other definitions for nutriment that I've seen before include "diet" , "Nourishing food" , "It sustains" , "Material providing food" , "Sustenance, nourishment" .)