Sound of a bird -- lark (4)
I believe the answer is:
hoot
'sound' is the definition.
(I have seen 'Sound of owl ' mean 'hoot' so perhaps 'sound' could also mean 'hoot')
'of a bird lark' is the wordplay.
I cannot quite see how this works, but
'of' could be 'o' and 'o' is present in 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 clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for hoot that I've seen before include "what's voiced in parliament?" , "Screech" , "Honk - laugh" , "Sound of owl" , "Owl's cry" .)