A professional can take a set quickly (6)
I believe the answer is:
presto
'quickly' is the definition.
(I've seen this before)
'a professional can take a set' is the wordplay.
'a professional' becomes 'pro' (abbreviation).
'can take' means one lot of letters goes inside another.
'a set' becomes 'est' (I am not sure about this - if you are sure you should believe this answer much more).
'pro' going around 'est' is 'PRESTO'.
Can you help me to learn more?
(Other definitions for presto that I've seen before include "Immediately" , "Very fast (mus.)" , "at great speed..." , "In a quick tempo (music)" , "hey......,cries the magician" .)