Supporter is behind what MPs do (9)

I believe the answer is:

legislate

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'supporter is behind what mps do' is the definition.
I can't tell whether this definition defines the answer.

'supporter is behind' is the wordplay.
'supporter' becomes 'leg' (I've seen this in another clue).
'behind' becomes 'late' (as in behind schedule).
'leg'+'is'+'late'='LEGISLATE'

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(Other definitions for legislate that I've seen before include "Make provision" , "For what governments do" , "what members do?" , "Establish rules" , "Pass through the house" .)

I've seen this clue in The Times.

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