Make a pick (6)
'make a pick' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for opt that I've seen before include "End or act of shutting" , "Choose from pot" , "Elect" , "Decide between possibilities, choose" , "Make a choice" .)
(Other definitions for choose that I've seen before include "Make a selection" , "Elect" , "So echo (anag) - wish" , "Select, opt for" , "Think fit" .)