Nest, one of four around top of elm (4)
I believe the answer is:
drey
'nest' is the definition.
(I know that drey is a type of nest)
'one of four around top of elm' is the wordplay.
'one of four' becomes 'dry' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'around' is an insertion indicator.
'top of' indicates taking the first letters.
The initial letter of 'elm' is 'e'.
'dry' going around 'e' is 'DREY'.
Can you help me to learn more?
(Other definitions for drey that I've seen before include "A squirrel's tree nest" , "Nest of a squirrel" .)