Happy to be dismissed by supply teacher producing stern reprimands (8)

I believe the answer is:

lectures

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'stern reprimands' is the definition.
'lectures' can be an answer for 'reprimands' (lecture is a kind of reprimand). I am not sure about the 'stern' bit.

'happy to be dismissed by supply teacher producing' is the wordplay.
'to be dismissed by' suggests deleting specific letters.
'producing' indicates anagramming the letters.
'supply'+'teacher'='supplyteacher'
'supplyteacher' with 'happy' taken away is 'sultecer'.
'sultecer' anagrammed gives 'LECTURES'.

Can you help me to learn more?

(Another definition for lectures that I've seen is " Discourses".)

I've seen this clue in The Irish Times.

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