British naturalist (6)
I believe the answer is:
darwin
<span class="explanation-format__ClueExplanation">'<span class="explanation-format__original">british naturalist</span>' is the definition.<br/ ><span class="explanation-format__explanation">(I've seen this in another clue)</span><br/ ><br/ >This is the entire clue.<br/ ></span>
(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" .)