Firstly, dunnocks and goldfinches, and siskins, robins, larks? (9)

I believe the answer is:

songbirds

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'firstly dunnocks and goldfinches' is the definition.
I can't tell whether this definition defines the answer.

'siskins robins larks?' is the wordplay.
'siskins robins' becomes 'song' (I am not sure about this - if you are sure you should believe this answer much more).
'larks?' becomes 'birds' (lark is a kind of bird).
'song'+'birds'='SONGBIRDS'

'and' acts as a link.

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