Redeveloped area until left by one side (10)

I believe the answer is:

unilateral

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'one side' is the definition.
Both the answer and definition are adjectives. Perhaps they are linked in a way I don't understand?

'redeveloped area until left' is the wordplay.
'redeveloped' indicates anagramming the letters.
'left' becomes 'l' (common abbreviation).
'area'+'until'='areauntil'
'areauntil' anagrammed gives 'unilatera'.
'unilatera'+'l'='UNILATERAL'

'by' is the link.

Can you help me to learn more?

(Other definitions for unilateral that I've seen before include "One-sided" , "Done only by one side" , "affecting only one person out of several" .)

I've seen this clue in The Independent.

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