Carefully examining wingless bird (5)
I believe the answer is:
robin
'bird' is the definition.
(I know that robin is a type of oscine)
'carefully examining wingless' is the wordplay.
'carefully' becomes 'rob' (I can't justify this - if you can you should give a lot more credence to this answer).
'examining' becomes 'sizing up' (sizing up is a kind of examining).
'wingless' indicates the central letters (the wings or sides of the letters are removed).
The centre of 'sizingup' is 'in'.
'rob'+'in'='ROBIN'
Can you help me to learn more?
(Other definitions for robin that I've seen before include ". . . . . Hood was a medieval outlaw" , "Day was one" , "Bird - boy's name" , "Famous outlaw" , "Hood, possibly" .)