Planter, we hear, for tree (5)
I believe the answer is:
cedar
'for tree' is the definition.
(cedar is a kind of tree)
'planter we hear' is the wordplay.
'planter' becomes 'seeder' (I've seen this in another clue).
'we hear' shows a homophone (sound like).
'seeder' sounds like 'CEDAR'.
(Other definitions for cedar that I've seen before include "may have needles?" , "Tall conifer" , "Tall coniferous tree" , "Tree giving fragrant wood" , "Evergreen tree" .)