Point to tree that's clean (4)
I believe the answer is:
wash
'clean' is the definition.
(washing is a kind of cleaning)
'point to tree' is the wordplay.
'point' becomes 'w' (West).
'to tree' becomes 'ash' (ash is a kind of tree).
'w'+'ash'='WASH'
'that's' acts as a link.
(Other definitions for wash that I've seen before include "Clean; dilute coat" , "Laundry" , "Of animals, cleanse by licking" , "Stand up" , "Lave" .)