Support for Tory PM no longer (5)

I believe the answer is:

truss

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'support' is the definition.
(type of architectural support)

I can't explain the remainder of the clue.

(Other definitions for truss that I've seen before include "Wing beam of a plane" , "Type of support" , "Bind - structural framework" , "Tie up tightly; frame" , "Frame supporting roof" .)

I've seen this clue in The Guardian.

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