Originator of theory's sore over hypothetical particle (7)
I believe the answer is:
tachyon
'particle' is the definition.
(hypothetical faster-than-light particle)
'originator of theory's sore over hypothetical' is the wordplay.
'originator of' suggests taking the first letters (I've seen 'originators of' mean this).
'sore' becomes 'achy' (I've seen this in another clue).
'over hypothetical' becomes 'on' (I can't explain this - if you can you should give a lot more credence to this answer).
The initial letter of 'theorys' is 't'.
't'+'achy'+'on'='TACHYON'
Can you help me to learn more?
(Another definition for tachyon that I've seen is " One moving faster than light".)