Choose something from the Top Twenty (3)
I believe the answer is:
opt
'choose' is the definition.
(both can mean to pick something)
'something from the top twenty' is the wordplay.
'something' indicates the answer is hidden within the clue (I've seen this in other clues).
'OPT' can be found hidden inside 'from top twenty'.
(Other definitions for opt that I've seen before include "Make a choice" , "Elect" , "Prefer, choose" , "Choose from pot" , "Pick from pot" .)