Some street-lining trees (4)
I believe the answer is:
elms
'some street-lining 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 "Trees (of late, prone to disease)" , "may have many leaves" , "Deciduous trees with rough serrated leaves" , "Mel's strange trees" , "Trees sound like Cockney steering devices" .)