Hold up fashionable bird (5)
I believe the answer is:
robin
'bird' is the definition.
(I know that robin is a type of oscine)
'hold up fashionable' is the wordplay.
'hold up' becomes 'rob' (as in holding up a bank).
'fashionable' becomes 'in' (in can mean fashionable or trendy).
'rob'+'in'='ROBIN'
(Other definitions for robin that I've seen before include "Red and brown songbird" , "Red-breasted songbird" , "Traditional Christmas card bird" , "Bird; Batman's aide" , "Small songbird" .)