Leave extremely disreputable sector (6)
I believe the answer is:
depart
'leave' is the definition.
(departing is a kind of leaving)
'extremely disreputable sector' is the wordplay.
'extremely' means to remove the middle letters.
'sector' becomes 'part' (both can mean a segment).
'disreputable' with its middle taken out is 'de'.
'de'+'part'='DEPART'
(Other definitions for depart that I've seen before include "Take one's leave, go" , "21" , "Set out" , "make tracks" , "Go away or leave" .)