Manage Charlie and posh bird (3,2)
I believe the answer is:
cut it
'manage' is the definition.
(to 'cut it' is to manage or cope in a situation)
'charlie and posh bird' is the wordplay.
'charlie' becomes 'c' (phonetic alphabet: alpha, bravo, charlie etc.).
'and' says to put letters next to each other.
'posh' becomes 'u' (abbreviation for upper-class - opposite to non-U).
'bird' becomes 'tit' (tit is a kind of bird).
'c'+'u'+'tit'='CUT IT'
(Other definitions for cut it that I've seen before include "manage" , "downsizing computer department?" , "Meet standards" , "Succeed" , "met requirements" .)