Hawthorn blossom could — possibly (3)
I believe the answer is:
may
I believe this is a double definition.
'hawthorn blossom' is the first definition.
(I've seen this before)
'could possibly' is the second definition.
(I've seen this in another clue)
(Other definitions for may that I've seen before include "Girl's name; 10 ac (anag.)" , "Fifth month" , "Has permission" , "UK PM" , "Time" .)