Son of Adam in Somerset House (4)
I believe the answer is:
seth
'son of adam' is the definition.
(I know that Seth father Adam)
'in somerset house' is the wordplay.
'in' says the answer is hidden in the clue.
'SETH' can be found hidden inside 'somerset house'.
(Other definitions for seth that I've seen before include "Cain and Abel's younger brother" , "Indian novelist, Vikram" , "Early man" , "Boy" , "Early human" .)