Crossword Genius

Sting to appear heartless — cocky type (5-4)

Ross

I believe the answer is:

smart-arse

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

'appear heartless cocky type' is the definition.
I know nothing about this answer so I cannot tell whether this works.

'sting to' is the wordplay.
'sting' becomes 'smart' (I've seen this before).
'to' becomes 'arse' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'smart'+'arse'='SMART-ARSE'

Can you help me to learn more?

I've seen this clue in The Guardian.
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