Old comedian's French knowledge (6,6)
I believe the answer is:
norman wisdom
'old comedian's' is the definition.
(comedy actor)
'french knowledge' is the wordplay.
'french' becomes 'norman' (Normandy is a part of France).
'knowledge' becomes 'wisdom' (wisdom is a kind of knowledge).
'norman'+'wisdom'='NORMAN WISDOM'
(Other definitions for norman wisdom that I've seen before include "English comic actor, famed for hapless on-screen roles, d. 2010" , "Pearls from Rouen, maybe" , "British comedian, once a cult figure in Albania, d. 2010" , "British comedic actor, 1915-2010" , "old actor" .)