Crossword Genius

What makes page dirty? A sort of bonk-lit (3-4)

Ross

I believe the answer is:

ink-blot

'what makes page dirty?' is the definition.
(a blot of ink would stain a page)

'a sort of bonk-lit' is the wordplay.
'a sort of' is an anagram indicator.
'bonk'+'lit'='bonklit'
'bonklit' is an anagram of 'INK-BLOT'.

I've seen this clue in The Guardian.
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