Flights of steps (6)
I believe the answer is:
stairs
'flights of steps' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for stairs that I've seen before include "A flight of indoor steps" , "Ascending flight of steps" , "4 and 8 (to the cockney)" , "Means of ascent/descent" , "Way between floors" .)