Like Matryoshka dolls (6)
I believe the answer is:
nested
'like matryoshka dolls' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for nested that I've seen before include "Inhabited an egg-laying place" , "Fitted inside one another, say set of tables" , "built a dwelling out of bits of wood" , "Of bird, settled in to home" , "intricate arrangement" .)