Birds, partridge, finally breaking cover (5)
I believe the answer is:
skein
'birds partridge finally breaking cover' is the definition.
I can't tell whether this definition defines the answer.
'partridge finally breaking cover' is the wordplay.
'finally' says to take the final letters.
'breaking' is an insertion indicator.
'cover' becomes 'skin' (skin is a kind of cover).
The final letter of 'partridge' is 'e'.
'e' placed within 'skin' is 'SKEIN'.
Can you help me to learn more?
(Other definitions for skein that I've seen before include "Coil of yarn - group of flying geese" , "Flight of birds" , "Hank" , "Loosely-coiled bundle of wool" , "Coil of wool - flock of geese" .)