Idly look through a book under a tree? (4)
I believe the answer is:
leaf
'tree?' is the definition.
The answer and definition can be both plants as well as being singular nouns.
Perhaps they are linked in a way I don't understand?
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for leaf that I've seen before include "See 1" , "needed for making a longer table" , "Page of a book" , "following 28 [SILVER]" , "Page; piece of tree" .)