Can seek to cut down tree (9)
I believe the answer is:
satinwood
'tree' is the definition.
(satinwood is a kind of tree)
'can seek to cut down' is the wordplay.
'can' becomes 'tin' (synonyms).
'seek' becomes 'woo' (to woo is to seek or pursue romantically).
'to cut' means one lot of letters goes inside another.
'down' becomes 'sad' (I've seen this before).
'tin'+'woo'='tinwoo'
'tinwoo' placed into 'sad' is 'SATINWOOD'.
(Other definitions for satinwood that I've seen before include "Cabinet material" , "Material valued for cabinetmaking" , "Hard material" , "Cabinetmaker's raw material" , "exotic tree?" .)