Biologist making racket about crazy war (6)
I believe the answer is:
'biologist' is the definition.
(Darwin is an example)
'racket about crazy war' is the wordplay.
'racket' becomes 'din' (both can mean a loud noise or disturbance).
'about' means one lot of letters goes inside another.
'crazy' is an anagram indicator.
'war' anagrammed gives 'arw'.
'din' placed around 'arw' is 'DARWIN'.
'making' is the link.
(Other definitions for darwin that I've seen before include "Charles ... who put forward theory of evolution" , "Author of The Descent of Man" , "He initiated the theory of evolution" , "English naturalist, Charles (1809-82)" , "Turn inward for the antipodean city" .)