Scientist creates original measure of weight (6)
I believe the answer is:
newton
'scientist' is the definition.
(Sir Isaac Newton)
'original measure of weight' is the wordplay.
I cannot really see how this works, but
'original' could be 'new' (similar in meaning) and 'new' is present in the answer.
'measure' could be 'ton' (ton is a kind of measure) and 'ton' is located in the answer.
No letters remain.
This explanation may well be incorrect...
'creates' is the link.
Can you help me to learn more?
(Other definitions for newton that I've seen before include "He is said to have discovered gravity" , "English mathematician and physicist, d. 1727" , "Great English mathematician who discovered gravity" , "Great English scientist who discovered gravity" , "Unit of force - English polymath, d. 1727" .)