Left state; on return had restriction (4)
I believe the answer is:
rein
This might be a double definition.
'left state on return' is the first definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'restriction' is the second definition.
(I've seen this before)
'had' is the link.
Can you help me to learn more?
(Other definitions for rein that I've seen before include "one's attached to a bit" , "Curb" , "leading article?" , "Restriction" , "Horse controller" .)