Crossword Genius

Bananas used with an indulgent treat (6)

Ross

I believe the answer is:

sundae

'indulgent treat' is the definition.
(type of ice cream)

'bananas used with an' is the wordplay.
'bananas' is an anagram indicator (informal term for mad).
'with' is a charade indicator (letters next to each other).
'used' after 'an' is 'anused'.
'anused' anagrammed gives 'SUNDAE'.

(Other definitions for sundae that I've seen before include "Type of ice-cream" , "Ice-cream/nut etc. dish" , "Ice cream with toppings" , "Ice cream served with a topping" , "Ice-cream dessert" .)

I've seen this clue in The Guardian.
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