You'll find him in probing a book of birds (5)
I believe the answer is:
robin
'you'll find him' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
'probing a book of birds' is the wordplay.
'ROBIN' is hidden within the letters.
But, I'm uncertain how the hidden word is indicated.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for robin that I've seen before include "Day was one" , "See 7" , "Batman and --" , "Small songbird" , "Bird - one in Lincoln green?" .)