Essentially legal, personal habit (4)
I believe the answer is:
gown
'habit' is the definition.
The answer and definition can be both man-made objects as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'essentially legal personal' is the wordplay.
'essentially' says to take the centre.
'personal' becomes 'own' (eg one's own possessions are personal possessions).
The middle of 'legal' is 'g'.
'g'+'own'='GOWN'
Can you help me to learn more?
(Other definitions for gown that I've seen before include "Formal frock, hospital garb and ceremonial dress" , "Loose dress or robe" , "Dress for formal occasions" , "Long formal dress" , "An evening dress" .)