Crossword Genius

Snout reported in prison public fully recognises (5,6,3)

Ross

I believe the answer is:

knows inside out

'fully recognises' is the definition.
(to know inside out is to fully understand)

'snout reported in prison public' is the wordplay.
'snout' becomes 'nose' (informal term for nose).
'reported' indicates a 'sounds like' (homophone) clue.
'in prison' becomes 'inside' (I've seen this before).
'public' becomes 'out' (I've seen this before).
'nose' sounds like 'knows'.
'knows'+'inside'+'out'='KNOWS INSIDE OUT'

I've seen this clue in The Telegraph.
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