A flight, of course, usually ends with a landing (6)
I believe the answer is:
stairs
'a landing' is the definition.
(thesaurus)
'a flight of course' is the wordplay.
'a flight' becomes 'stair' (I've seen this before).
'of course' becomes 's' (I can't explain this - if you can you should believe this answer much more).
'stair'+'s'='STAIRS'
'usually ends with' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for stairs that I've seen before include "Access consisting of steps" , "Series of steps" , "Ascending flight of steps" , "Means of ascent/descent" , "A flight of indoor steps" .)