Rather younger elder? (7)
I believe the answer is:
sapling
'rather younger elder?' is the definition.
(a sapling is a young tree, eg an elder tree)
This is all the clue.
(Other definitions for sapling that I've seen before include "Young slender tree" , "Lapsing into a young tree" , "Little tree" , "Baby tree" , "Poetic youth" .)