Your basic make-up is foundation (7)
I believe the answer is:
genesis
'foundation' is the definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.
'your basic make-up is' is the wordplay.
I cannot quite see how this works, but
'is' is found in the answer.
The remaining letters 'genes' is a valid word which might be clued in a way I don't see.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for genesis that I've seen before include "Old Testament Book 1" , "Beginning (in the Bible)" , "Origin -- see sign (anag)" , "First book of the Bible" , "Birth, beginnings" .)