Guilt concerning Oxford inspector (7)
I believe the answer is:
remorse
'guilt' is the definition.
(feeling guilty)
'concerning oxford inspector' is the wordplay.
I cannot quite see how this works, but
'concerning' could be 're' (both can mean on a particular topic) and 're' is present in the answer.
'inspector' could be 'morse' (Inspector Morse) and 'morse' is found in the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for remorse that I've seen before include "regrets" , "Ruefulness" , "Pity" , "Bitter regret" , "Gnawing pain of conscience" .)