Vocally relish Genesis? (6)
I believe the answer is:
source
'genesis?' is the definition.
(source is a kind of genesis)
'vocally relish' is the wordplay.
'vocally' indicates a 'sounds like' (homophone) clue.
'relish' becomes 'sauce' (relish can mean a sauce or dressing).
'sauce' is a homophone of 'SOURCE'.
(Other definitions for source that I've seen before include "Origin as of a river" , "From which something springs" , "Spring, fountain head" , "Where something originates" , "Origin, starting-point" .)