One on at Edinburgh holds baby (7)
I believe the answer is:
neonate
'baby' is the definition.
(medical term for a newborn child)
'one on at edinburgh holds' is the wordplay.
'holds' says the answer is hidden in the clue.
'NEONATE' is hidden within 'one on at edinburgh'.
(Other definitions for neonate that I've seen before include "Recently born child" , "Young infant" , "Newborn baby" , "produced baby" , "New baby" .)