Rocky boulder is revealing avian pest (4-5)

I believe the answer is:

bird-louse

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'avian pest' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how one could define the other.

'rocky boulder is' is the wordplay.
'rocky' indicates an anagram (letters rocked or thrown around).
'boulder'+'is'='boulderis'
'boulderis' anagrammed gives 'BIRD-LOUSE'.

'revealing' is the link.

Can you help me to learn more?

I've seen this clue in The Independent.

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