John Henry in Bar providing legal oversight (8)
I believe the answer is:
loophole
'legal oversight' is the definition.
Although both the answer and definition are singular nouns, I don't understand how one could define the other.
'john henry in bar' is the wordplay.
'john' becomes 'loo' (both can mean a toilet).
'henry' becomes 'H' (symbol for the unit of electrical inductance).
'in' means one lot of letters goes inside another.
'bar' becomes 'pole' ().
'h' going within 'pole' is 'phole'.
'loo'+'phole'='LOOPHOLE'
'providing' is the link.
Can you help me to learn more?
(Other definitions for loophole that I've seen before include "Exploitable ambiguity" , "Mistake in legislation" , "Get-out" , "unplanned escape" , "opening" .)