Foliage left on the edges of the roof (6)
I believe the answer is:
leaves
'foliage' is the definition.
(I've seen this in another clue)
'left on the edges of the roof' is the wordplay.
'left' becomes 'l' (common abbreviation).
'on' means one lot of letters go next to another (in a down clue, letters appear on others).
'the edges of the roof' becomes 'eaves' (I can't explain this - if you can you should believe this answer much more).
'l'+'eaves'='LEAVES'
Can you help me to learn more?
(Other definitions for leaves that I've seen before include "exits" , "Departs with tree growths" , "Organs of photosynthesis" , "Departs with book pages?" , "They are found on trees and in books" .)