Scientist went on rambling (6)
I believe the answer is:
newton
'scientist' is the definition.
(Sir Isaac Newton)
'went on rambling' is the wordplay.
'rambling' is an anagram indicator.
'went'+'on'='wenton'
'wenton' is an anagram of 'NEWTON'.
(Other definitions for newton that I've seen before include "Supposedly, an apple fell on his head" , "Explainer of gravity" , "inclined to apply discovery?" , "Great English mathematician who discovered gravity" , "He is said to have discovered gravity" .)