Support is rising, light the explosive! (9)

I believe the answer is:

gelignite

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'explosive' is the definition.
(gelignite is a kind of explosive)

I can't explain the remainder of the clue.

(Other definitions for gelignite that I've seen before include "Explosive used in mining" , "factor in altering mine?" , "source of flare-up" , "High explosive" , "(E.g. quarry) explosive" .)

I've seen this clue in The Telegraph.

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