Restorative instilling energy before noon in first-year student (9)
I believe the answer is:
freshener
'restorative instilling' is the definition.
The definition suggests a singular noun which matches the answer.
'energy before noon in first-year student' is the wordplay.
'energy' becomes 'e' (physics symbol as in E=mcr).
'before' means one lot of letters go next to another.
'noon' becomes 'n' (abbreviation).
'in' means one lot of letters goes inside another.
'first-year student' becomes 'fresher' (I've seen this before).
'e'+'n'='en'
'en' inserted inside 'fresher' is 'FRESHENER'.
Can you help me to learn more?
(Other definitions for freshener that I've seen before include "deodorant?" , "Something making pleasantly clean" , "stimulant" .)