Crossword Genius

Principal state short of energy

Ross

I believe the answer is:

main

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This could be a double definition.

'principal' is the first definition.
(I know that principal can be written as main)

'state short of energy' is the second definition.
'main' can be an answer for 'energy' (thesaurus). I am unsure of the 'state short of' bit.

Can you help me to learn more?

(Other definitions for main that I've seen before include "Chief in importance" , "one might expect tap water from it" , "(The mighty) sea" , "Most important - high seas?" , "Source of electricity" .)

I've seen this clue in The Daily Mail.
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