Regularly we climb tree (3)
I believe the answer is:
Here is my best explanation:
'tree' is the definition.
(elm is a kind of tree)
'regularly we climb' is the subsidiary indication.
'regularly' means one should take alternating letters (regularly take one letter, leave next etc.).
The alternate letters of 'weclimb' are 'elm'.
(Other definitions for elm that I've seen before include "Furniture wood", "I branch out", "Leaving body", "wood used in pelmets", "Tree of the genus Ulmus", "Mel's tree", "It provides shade", "Forest tree", "Tall shade tree" and "Kind of tree".)