Energy-fuelled blast in Hell (5)

I believe the answer is:

below

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'in hell' is the definition.
(thesaurus)

I don't understand the remainder of the clue.

(Other definitions for below that I've seen before include "Beneath" , "in one's cabin" , "Not worthy of" , "Later in text" , "Subordinate to" .)

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

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