Some could help a man to climb a tree (5)
I believe the answer is:
maple
'a tree' is the definition.
(maple is a kind of tree)
'some could help a man to climb' is the wordplay.
'some' indicates a hidden word (some parts of the word are used).
'to climb' says the letters should be written in reverse (I've seen 'climbs' mean this).
'elpam' can be found hidden inside 'could help a man'.
'elpam' back-to-front is 'MAPLE'.
(Other definitions for maple that I've seen before include "Tree providing syrup" , "Its leaf is the emblem of 8 down" , "Tree; sauce" , "Tree with winged seeds" , "Hard light-coloured wood used for furniture" .)