Slippery round the edge (3)

I believe the answer is:

lip

I'm a little stuck... Click here to teach me more about this clue!

'the edge' is the definition.
(lip is a kind of edge)

'slippery round' is the wordplay.
'LIP' is hidden in amongst the letters.
But, I'm unsure how this is indicated.

Can you help me to learn more?

(Other definitions for lip that I've seen before include "Rim; impertinence" , "Rim of an orifice" , "Fleshy fold of mouth tissue" , "Brink" , "Insolence (slang)" .)

I've seen this clue in The Mirror.

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