Certain shade trees (4)
I believe the answer is:
elms
'certain shade trees' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for elms that I've seen before include "Mel's strange trees" , "may have many leaves" , "Deciduous trees with rough serrated leaves" , "Trees (of late, prone to disease)" , "Trees sound like Cockney steering devices" .)