The most common and most likely answer to this crossword clue is the 14 letter word ELECTROSTATICS
I've seen this crossword clue in Independent
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Buddy explains!
The straight part
We know that "some bit of physics" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case some bit of physics = electrostatics.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does ELECTROSTATICS mean?
ELECTROSTATICS noun- The branch of physics that deals with static electricity; that is, with the force exerted by an unchanging electric field upon a charged object