School lied about the old pupil, protected by this (6)
I believe the answer is:
eyelid
'pupil protected by this' is the definition.
The definition suggests a singular noun which matches the answer.
'school lied about the old' is the wordplay.
'school' indicates anagramming the letters (school can mean to improve or manipulate).
'about' is an insertion indicator.
'the old' becomes 'ye' (resembles a historical spelling of 'the').
'lied' anagrammed gives 'elid'.
'elid' going around 'ye' is 'EYELID'.
Can you help me to learn more?
(Other definitions for eyelid that I've seen before include "Blinking cover" , "Fold of skin on the face" , "Facial feature" , "Optic membrane" , "Cover for organ of sight" .)