It's laid across the line of flight (5,3)
I believe the answer is:
stair rod
'it's laid' is the definition.
I can't tell whether this defines the answer.
'across the line of flight' is the wordplay.
'across' is a charade indicator (letters next to each other) (across can mean on).
'the line of' becomes 'rod' (I can't justify this - if you can you should believe this answer much more).
'flight' becomes 'stair' (I've seen this before).
'rod' put after 'stair' is 'STAIR-ROD'.
Can you help me to learn more?
(Other definitions for stair rod that I've seen before include "Securer for carpet" , "it might pour this" , "As torrid (anag.)" , "seeming to come down in heavy rain" , "Fixture between riser and treader" .)