British naturalist (6)
I believe the answer is:
darwin
'british naturalist' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for darwin that I've seen before include "Charles ... who put forward theory of evolution" , "Charles . . . . . ., author of 'The Origin of Species'" , "Charles . . . . . ., great scientist of evolution" , "I'd warn this natural scientist" , "Aus. N. Territory capital" .)