Kelly or Wilder (4)
I believe the answer is:
gene
I believe this clue is a double definition.
'kelly' is the first definition.
(I've seen this in another clue)
'wilder' is the second definition.
(gene wilder)
(Other definitions for gene that I've seen before include "may be passed to child" , "Part of chromosome" , "- - Kelly, dancer" , "Bodily factor controlling heredity" , "Hereditary determinant" .)