Things lying about untidily (7)
I believe the answer is:
clutter
'things lying about untidily' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for clutter that I've seen before include "Untidy mess" , "Untidy lot of objects in room" , "Confused muddle of things" , "Disorderly mess" , "Things lying about untidily" .)