Scientist using different unit of weight (6)
I believe the answer is:
newton
'scientist' is the definition.
(Newton is an example)
'different unit of weight' is the wordplay.
'different' becomes 'new' ('new' can be similar in meaning to 'different').
'unit of weight' becomes 'ton' (I've seen this before).
'new'+'ton'='NEWTON'
'using' is the link.
(Other definitions for newton that I've seen before include "He is said to have discovered gravity" , "inclined to apply discovery?" , "SI unit of force" , "Sir Isaac . . . . . ., great English mathematician" , "Thandie - - , actress" .)