Some discovered leaves up a tree (5)
I believe the answer is:
elder
'a tree' is the definition.
(elder is a kind of tree)
'some discovered leaves up' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'up' shows that the letters should be reversed in order (in down clue: letters go upwards).
'redle' can be found hidden inside 'discovered leaves'.
'redle' reversed gives 'ELDER'.
(Other definitions for elder that I've seen before include "More aged; tree" , "Tribal leader; tree" , "Senior - church official" , "Senior leader" , "Tree - wise counsellor" .)