Smarty-pants, cold, the French musician, vacuous crook (6,4)
I believe the answer is:
clever dick
'smarty-pants' is the definition.
'cold the french musician vacuous crook' is the wordplay.
'cold' becomes 'c' (eg on taps).
'the french' becomes 'le' ('the' in French).
'musician' becomes 'verdi' (Giuseppe Verdi 1813-1901).
'vacuous' means to remove the middle letters.
'crook' with its middle taken out is 'ck'.
'c'+'le'+'verdi'+'ck'='CLEVER DICK'
(Other definitions for clever dick that I've seen before include "Know-all" , "The one with all the answers" , "Wise guy" .)