Note lithe mountaineer (7)
I believe the answer is:
climber
'mountaineer' is the definition.
(someone climbing mountains)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for climber that I've seen before include "Mountaineer" , "in the garden" , "Plant such as ivy" , "Edward Whymper, for example" , "Plant that grows up a support" .)