Sing about ease in vision (6)
I believe the answer is:
seeing
'vision' is the definition.
(vision is the ability to see)
'sing about ease' is the wordplay.
'about' indicates putting letters inside.
'ease' becomes 'ee' (I've seen this in other clues).
'sing' enclosing 'ee' is 'SEEING'.
'in' is the link.
(Other definitions for seeing that I've seen before include "Watching" , "Vision" , "... is believing, it's said" , "Spotting - interviewing" , "since" .)