Crossword Genius

"Tea" with mum's sister Barb (5)

Ross

I believe the answer is:

taunt

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

'barb' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.

'tea with mum's sister' is the wordplay.
'tea' becomes 't' (I've seen this in other clues).
'with' is a charade indicator (letters next to each other).
'mum's sister' becomes 'aunt' (I can't explain this - if you can you should believe this answer much more).
't'+'aunt'='TAUNT'

Can you help me to learn more?

(Other definitions for taunt that I've seen before include "Thing said to anger or wound" , "Mock provokingly" , "Sarcastic challenge" , "Mock, jeer" , "Jeer, deride" .)

I've seen this clue in the Sydney Morning Herald.
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