Schoolmaster's first sign about new items in lunch boxes (7)
I believe the answer is:
sarnies
'items in lunch boxes' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.
'schoolmaster's first sign about new' is the wordplay.
'schoolmaster's first' becomes 's' (1st letter of 'schoolmaster').
'sign' becomes 'aries' (star sign).
'about' means one lot of letters goes inside another.
'new' becomes 'n'.
'aries' placed around 'n' is 'arnies'.
's'+'arnies'='SARNIES'
Can you help me to learn more?
(Another definition for sarnies that I've seen is " Snacks".)