In outskirts of Namur, a detective’s lowest point (5)
I believe the answer is:
nadir
'lowest point' is the definition.
'in outskirts of namur a detective's' is the wordplay.
'in' indicates putting letters inside.
'outskirts of' suggests removing the centre.
'detective' becomes 'di' (Detective Inspector abbreviation).
'namur' with its centre taken out is 'nr'.
'a'+'di'='adi'
'nr' going around 'adi' is 'NADIR'.
(Other definitions for nadir that I've seen before include "Drain (anag)" , "least successful point" , "You can't sink lower!" , "Drain into the lowest point (5)" , "businessman formerly escaping justice" .)