Chance to miss opening in one bird's call or another's (6)
I believe the answer is:
cuckoo
'bird's call or another's' is the definition.
I can't judge whether this defines the answer.
'chance to miss opening in one' is the wordplay.
'chance' becomes 'luck' (synonyms).
'to miss opening' means to remove the first letter (I've seen 'missing opening' mean this).
'in' means one lot of letters goes inside another.
'one' becomes 'coo' (I can't explain this - if you can you should give a lot more credence to this answer).
'luck' with its first letter taken off is 'uck'.
'uck' going within 'coo' is 'CUCKOO'.
Can you help me to learn more?
(Other definitions for cuckoo that I've seen before include "Is the brown bird daft?" , "nuts" , "that can emerge at hourly intervals" , "Bird; sort of clock" , "Onomatopoeic bird" .)