Accuracy is maintained by compass (7)
I believe the answer is:
realism
'compass' is the 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 don't see?
'accuracy is maintained' is the wordplay.
'accuracy' becomes 'realm' (I can't explain this - if you can you should give a lot more credence to this answer).
'maintained' means one lot of letters goes inside another (inserted letters get controlled or maintained).
'realm' placed around 'is' is 'REALISM'.
'by' acts as a link.
Can you help me to learn more?
(Other definitions for realism that I've seen before include "Practical quality" , "Practical approach" , "Acceptance of life as it is" , "Artistic movement representing people and things as they actually are" , "True-to-life quality" .)