He, as a qualified judge, about to discharge European detained (7)
I believe the answer is:
referee
'he as a qualified judge' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'about to discharge european detained' is the wordplay.
I cannot quite see how this works, but
'about' could be 're' ('re' means regarding or about) and 're' is located in the answer.
'european' could be 'e' (abbreviation e.g. EU) and 'e' is found in the answer.
'discharge' could be 'free' (synonyms) and 'free' is found in the remaining letters.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for referee that I've seen before include "Judge" , "Sports adjudicator" , "Umpire; arbitrator" , "Football official" , "Sports official" .)