They're for the birds (5)
I believe the answer is:
nests
'they're for the birds' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for nests that I've seen before include "Tables made to fit closely together" , "Sets of small tables that fit closely together" , "Eyries" , "Structures for laying eggs" , "Places to rear the young?" .)