Coat's second layer worn by 'umble character (9)
I believe the answer is:
sheepskin
'coat's' is the definition.
(sheepskin coat is a kind of coat)
'second layer worn by 'umble character' is the wordplay.
I cannot quite see how this works, but
'second' could be 's' (common abbreviation) and 's' is present in the answer.
'layer' could be 'skin' (I have seen 'Outer layer ' mean 'skin' so perhaps 'layer' could also mean 'skin') and 'skin' is present in the answer.
'character' could be 'he' (he is a kind of letter of the alphabet) and 'he' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for sheepskin that I've seen before include "Ovine outer layer used in coats and rugs" , "Fleece garment" , "leather" , "Woolly pelt" , "coat" .)