Bay or plane, say (4)
I believe the answer is:
I believe this is a double definition.
'bay' is the first definition.
'plane say' is the second definition.
(plane is a type of tree)
(Other definitions for tree that I've seen before include "Christmas decoration" , "Care for shoes" , "Recently named grouping of rogue states" , "Root-and-branch plant?" , "Plant with a main trunk and branches" .)