One-time supporter in the case of there being a member short (6,3)

I believe the answer is:

wooden leg

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'the case of there being a member short' is the definition.
I can't tell whether this defines the answer.

'one-time supporter' is the wordplay.
'one time' becomes 'wooden' (I am not sure about this - if you are sure you should believe this answer much more).
'supporter' becomes 'leg' (eg support for a table).
'wooden'+'leg'='WOODEN LEG'

'in' is the link.

Can you help me to learn more?

(Other definitions for wooden leg that I've seen before include "Eight lines of verse" , "Walk-on part" .)

I've seen this clue in the Evening Standard.

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