A climbing aid, naturally (7)
I believe the answer is:
tendril
'a climbing' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'aid naturally' is the wordplay.
I cannot quite see how this works, but
'aid' could be 'tend' and 'tend' is found in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for tendril that I've seen before include "Plant's climbing aid" , "Climbing plant's attachment" , "Slender stem on twining plants" , "Plant extrusion" , "Slender structure on some twining plants" .)