Tree on coast, possibly, or shrub? (11)
I believe the answer is:
Here is my best explanation:
'shrub?' is the definition.
(cotoneaster is a kind of shrub)
'tree on coast possibly' is the subsidiary indication.
'possibly' indicates an anagram.
'treeoncoast' with letters rearranged gives 'cotoneaster'.
'or' is the link.
(Other definitions for cotoneaster that I've seen before include "Red-berried garden shrub", "Shrub with red berries", "shrub with berries" and "Plant".)