Like some bears hiding quietly in tree (6)
I believe the answer is:
poplar
'tree' is the definition.
(I know that poplar is a type of angiospermous tree)
'like some bears hiding quietly' is the wordplay.
'like some bears' becomes 'polar' (I've seen this in another clue).
'hiding' indicates putting letters inside.
'quietly' becomes 'p' (musical symbol).
'polar' going around 'p' is 'POPLAR'.
'in' acts as a link.
(Other definitions for poplar that I've seen before include "Tree with leaves that quiver" , "Slender tree with quivering leaves" , "Deciduous tree" , "The tree is almost liked" , "Tall fast-growing tree; East London area" .)