Darwin's even got a beard! (3)
I believe the answer is:
awn
'a beard' is the definition.
(both can mean a growth on plants)
'darwin's even' is the wordplay.
'even' means one should take alternating letters (letters in even-numbered positions are used).
The alternating letters of 'darwins' are 'AWN'.
'got' acts as a link.
(Other definitions for awn that I've seen before include "Stiff bristle on grasses" , "bit of cereal" , "Bristle in flowering part of some grasses" , "Bristles" , "Bristle on grass spikelet" .)