Close to fastening negligee (7)
I believe the answer is:
nightie
'fastening negligee' 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 can't see?
'close to' is the wordplay.
'close' becomes 'nigh' (similar in meaning).
'to' becomes 'tie' (I can't explain this - if you can you should give a lot more credence to this answer).
'nigh'+'tie'='NIGHTIE'
Can you help me to learn more?
(Other definitions for nightie that I've seen before include "garment worn in bed" , "Skimpy attire" , "Woman's bedwear" , "Female bedwear" , "Lingerie item" .)