Crossword Genius

Light-headed age? (5)

Ross

I believe the answer is:

fifty

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'light-headed age?' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.

This is the entire clue.

Can you help me to learn more?

(Other definitions for fifty that I've seen before include "L" , "A multiple of ten" , "Half-century" .)

I've seen this clue in the Evening Standard.
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