Genetic stuff
I believe the answer is:
dna
'genetic stuff' is the definition.
(DNA is genetic material)
This is all the clue.
(Other definitions for dna that I've seen before include "Deoxyribonucleic acid (abbreviation)" , "Main constituent of chromosomes" , "Substance in chromosomes that stores genetic information, used by police" , "Bodily substance that stores genetic information - police use it to identify" , "Genetic carrier" .)