Light-headed as my aunt? (5)

I believe the answer is:

giddy

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'light-headed' is the definition.
(I know that lightheaded can be written as giddy)

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

Can you help me to learn more?

(Other definitions for giddy that I've seen before include "Dizzy or frivoloous" , "Light-headed; unable to balance" , "Suffering from vertigo" , "Flighty, frivolous" , "Sturdy" .)

I've seen this clue in The Sun.

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