Never-ending road heading west round twisted stunted tree (7)
I believe the answer is:
eternal
'never-ending' is the definition.
(both can mean lasting forever)
'road heading west round twisted stunted tree' is the wordplay.
'road' becomes 'lane' (a lane is a small road).
'heading west' says the letters should be written in reverse.
'round' indicates putting letters inside.
'twisted' indicates an anagram.
'stunted' means to remove the last letter (the word is shorter than it usually is).
'lane' backwards is 'enal'.
'tree' with its final letter taken off is 'tre'.
'tre' anagrammed gives 'ter'.
'enal' enclosing 'ter' is 'ETERNAL'.
(Other definitions for eternal that I've seen before include "Forever and always" , "Forever or unchanging" , "Infinite - endless" , "'Lasting forever, unending (7)'" , "Ceaseless" .)