Sounding angry if girl gets basic schooling requirement (4)

I believe the answer is:

grrr

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'sounding angry' is the definition.
I know nothing about this answer so I can't judge whether it can be defined by this definition.

'girl gets basic schooling requirement' is the wordplay.
'girl' becomes 'g'.
'gets' is a charade indicator (letters next to each other).
'basic schooling requirement' becomes 'rrr' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'g'+'rrr'='GRRR'

'if' acts as a link.

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I've seen this clue in The Irish Times.

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