Birch family members (6)
I believe the answer is:
alders
'birch family members' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for alders that I've seen before include "Al's red trees, strangely" , "Trees for red Sal" , "Trees with toothed leaves" , "Trees of the birch family" , "Catkin-bearing trees" .)