Needing support, being half unpinned (3-6)

I believe the answer is:

one-legged

'needing support' is the definition.

'half unpinned' is the wordplay.
'half' becomes 'one' (I have seen 'Half of two ' mean 'one' so perhaps 'half' could also mean 'one').
'unpinned' becomes 'legged' (I can't explain this - if you can you should believe this answer much more).
'one'+'legged'='ONE-LEGGED'

'being' acts as a link.

(Another definition for one-legged that I've seen is " Having but a single pin".)

I've seen this clue in The Guardian.

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