Heard birdcall through felt lid (6)
I believe the answer is:
trilby
'lid' is the definition.
(I know that trilby is a type of lid)
'heard birdcall through felt' is the wordplay.
I cannot quite see how this works, but
'through' could be 'by' and 'by' is found in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for trilby that I've seen before include "Soft hat with indented crown" , "du Maurier's heroine" , "Book by George du Maurier - hat" , "Impressionable singer" , "Sinatra's hat?" .)