Horrible wasting energy - there's a lot of it (6)

I believe the answer is:

hatful

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'lot of it' is the definition.
'hatful' can be an answer for 'lot' (I've seen this before). I'm not sure about the 'of it' bit.

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for hatful that I've seen before include "Large number" , "lot" .)

I've seen this clue in The Irish Times.

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