A help or a hindrance in the works (7)
I believe the answer is:
spanner
'hindrance in the works' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Perhaps there's a link between them I don't understand?
'a help or a' is the wordplay.
I cannot quite see how this works, but
'a' could be 'an' and 'an' is located in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for spanner that I've seen before include "Nut turner" , "Nut tightener" , "Wrench for nuts" , "Nut-tightening tool" , "In the works, this tool is an obstacle" .)