Why this clue should tickle yours, is not plain! (5)

I believe the answer is:

fancy

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'is not plain' is the definition.
('fancy' is the opposite to 'plain')

I don't understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for fancy that I've seen before include "Highly-decorated; whim" , "Imagine - whim - highly decorated" , "Imagine - find attractive" , "Ornamented" , "Unfounded belief" .)

I've seen this clue in the Evening Standard.

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