Comprehensive physics explanation: digit at the base of everything (3)

I believe the answer is:

toe

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'comprehensive physics explanation digit' is the definition.
I can't judge whether this definition defines the answer.

'the base of everything' is the wordplay.
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'base' indicates taking the first letters (I've seen 'base of' mean this).
The first letters of 'of everything' is 'oe'.
't'+'oe'='TOE'

'at' acts as a link.

Can you help me to learn more?

(Other definitions for toe that I've seen before include "A foot division" , "'Little piggy'" , "End of sock" , "Lower tip of something" , "Extremity of the body" .)

I've seen this clue in The Independent.

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