Magnificent craft going over tree (7)
I believe the answer is:
sublime
'magnificent' is the definition.
(I've seen this before)
'craft going over tree' is the wordplay.
'craft' becomes 'sub' (sub is a kind of craft).
'going over' means one lot of letters go next to another.
'tree' becomes 'lime' (type of tree).
'sub'+'lime'='SUBLIME'
(Other definitions for sublime that I've seen before include "Wonderful" , "Awe-inspiring - exalted" , "Glorious; supreme" , "Heavenly" , "Unparalleled, extreme" .)