Origin of burger meat (4)
I believe the answer is:
germ
'origin' is the definition.
(germ is a kind of origin)
'of burger meat' is the wordplay.
'of' says the answer is hidden in the clue.
'GERM' is hidden within 'burger meat'.
(Other definitions for germ that I've seen before include "infectious organism" , "Bug" , "starting point" , "Cause of disease" , "From which disease comes" .)