Strengthened, nonetheless hairy? (10)

I believe the answer is:

buttressed

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'strengthened' is the definition.
(buttressing is a kind of strengthening)

'nonetheless hairy?' is the wordplay.
'nonetheless' becomes 'but' (I've seen this in another clue).
'hairy?' becomes 'tressed' (I can't explain this - if you can you should believe this answer much more).
'but'+'tressed'='BUTTRESSED'

Can you help me to learn more?

(Other definitions for buttressed that I've seen before include "held securely" , "Supported" , "Reinforced" .)

I've seen this clue in The Everyman puzzle in The Observer.

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