Part of the foliage of a maple, a fir, etc. (4)
I believe the answer is:
leaf
'part of the foliage' is the definition.
'leaf' can be an answer for 'foliage' (synonyms). I'm not sure about the 'part of the' bit.
'of a maple a fir etc' is the wordplay.
'of' says the answer is hidden in the clue.
'LEAF' can be found hidden inside 'maple a fir etc'.
Can you help me to learn more?
(Other definitions for leaf that I've seen before include "Part of a plant and of a book" , "Two pages of a book" , "Bit of tree, of book" , "In fall, one dislocated" , "Hinged or removable table flap" .)