Leave day before tree's destroyed (6)
I believe the answer is:
desert
'leave' is the definition.
(deserting is a kind of leaving)
'day before tree's destroyed' is the wordplay.
'day' becomes 'd' (**).
'before' says to put letters next to each other.
'destroyed' indicates an anagram.
'trees' with letters rearranged gives 'esert'.
'd'+'esert'='DESERT'
(Other definitions for desert that I've seen before include "Treacherously abandon" , "Wild" , "Abandon in wasteland" , "Arid area of sand" , "expanse of land without water" .)