One who holds an inquest finding nothing in nook (7)
I believe the answer is:
coroner
'one who holds an inquest' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'nothing in nook' is the wordplay.
'nothing' becomes 'O' (O resembles 0).
'in' means one lot of letters goes inside another.
'nook' becomes 'corner' (synonyms).
'o' going into 'corner' is 'CORONER'.
'finding' is the link.
Can you help me to learn more?
(Other definitions for coroner that I've seen before include "Official who investigates sudden deaths" , "Inquest holder" , "Official enquiring into any death" , "Investigator" , "Medico-legal officer" .)