Part of tree containing small place for rest of birds (5)

I believe the answer is:
roost
'for rest of birds' is the definition.
I can't tell whether this defines the answer.
'part of tree containing small' is the wordplay.
'part of tree' becomes 'root' (trees have roots).
'containing' indicates putting letters inside.
'small' becomes 's' (abbreviation - e.g. clothes size).
'root' enclosing 's' is 'ROOST'.
'place' is the link.
Can you help me to learn more?
(Other definitions for roost that I've seen before include "Thin paper" , "Hen house; perch" , "bed" , "Where birds rest at night" , "Settle down (on a branch?)" .)
