Guiding light to join Tories? (6)

I believe the answer is:

beacon

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'guiding light' is the definition.
(I've seen this in another clue)

I can't explain the rest of the clue.

(Other definitions for beacon that I've seen before include "Warning light on tower or hill" , "Shiner" , "Hill fire seen from a distance" , "Warning light in the distance" , "warning to others" .)

I've seen this clue in The Telegraph and The Sun.

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