A sound one may not give (4)
I believe the answer is:
hoot
'a sound' is the definition.
(I have seen 'Sound of owl ' mean 'hoot' so perhaps 'sound' could also mean 'hoot')
'one may not give' is the wordplay.
I cannot quite see how this works, but
'not' could be 'o' (I've seen this in other clues) and 'o' is found within the answer.
The remaining letters 'hot' is a valid word which might be clued in a way I don't see.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for hoot that I've seen before include "scream" , "Owl's sound" , "Owlish cry" , "On (a ship/train/plane)" , "Screech" .)