Newton, for one, claims the ground (9)
I believe the answer is:
alchemist
'newton' is the definition.
The definition and answer can be both people as well as being singular nouns.
Perhaps you can see an association between them that I don't see?
'one claims the ground' is the wordplay.
'ground' is an anagram indicator ('grind' the letters into a new form).
'claims'+'the'='claimsthe'
'claimsthe' with letters rearranged gives 'ALCHEMIST'.
'for' acts as a link.
Can you help me to learn more?
(Other definitions for alchemist that I've seen before include "Seeker after gold" , "one trying to find the elixir of life" , "... seeker after stone" , "Medieval experimenter" , "such as Paracelsus" .)