Character builder? (4)
I believe the answer is:
gene
'character builder?' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for gene that I've seen before include "Hereditary DNA sequence" , "Bodily factor controlling heredity" , "Vincent" , "Something got from parent < for boy" , "___ Kelly, star of Singin' In The Rain, d. 1996" .)