Pick great joke, forgetting the opening (5)
I believe the answer is:
cream
'pick' is the definition.
('cream' can be a synonym of 'pick')
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for cream that I've seen before include "Dairy product" , "Best - substitute for shaving soap" , "treat for cat?" , "Butterfat part of milk" , "The best part -of the crop" .)