Try to appropriate all the biggest (7)

I believe the answer is:

tallest

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'biggest' is the definition.
Both the definition and answer are superlative adjectives. Maybe you can see an association between them that I can't see?

I can't explain the rest of the clue.

Can you help me to learn more?

(Other definitions for tallest that I've seen before include "most unlikely" , "Highest in stature" , "Sell tat (anag.)" , "Of greatest vertical extent" , "Of greatest height" .)

I've seen this clue in the Evening Standard.

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