Settle (on) (6)
'settle on' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for choose that I've seen before include "Select, opt for" , "Think fit" , "Elect" , "Make a selection" , "Pick, select." .)
(Other definitions for alight that I've seen before include "Step off the bus because it's on fire?" , "Land, come down" , "Small restaurant" , "Touch down" , "following action of arsonist?" .)