Tree for the seashore we hear (5)
I believe the answer is:
beech
'tree' is the definition.
(I know that beech is a type of tree)
'seashore we hear' is the wordplay.
'seashore' becomes 'beach' (I've seen this before).
'we hear' shows a homophone (sound like).
'beach' is a homophone of 'BEECH'.
'for the' acts as a link.
(Other definitions for beech that I've seen before include "Nut-bearing tree" , "Tree variety" , "Deciduous tree with smooth grey bark" , "Tree of Fagus genus" , "Common deciduous tree" .)