Crossword Genius

Mug up on grammar — potty, potty (5)

Ross

I believe the answer is:

typto

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'mug up on grammar' is the definition.
I know nothing about this answer so I cannot judge whether it can be defined by this definition.

'potty potty' is the wordplay.
'potty' is an anagram indicator.
'potty' anagrammed gives 'TYPTO'.

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I've seen this clue in The Times.
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