Escort booting out husband who’s on drugs (4)
I believe the answer is:
user
'who's on drugs' is the definition.
(someone who uses drugs)
'escort booting out husband' is the wordplay.
'escort' becomes 'usher' (usher is a kind of escort).
'booting out' is a deletion indicator.
'husband' becomes 'h'.
'usher' with 'h' taken out is 'USER'.
(Other definitions for user that I've seen before include "One getting benefit from" , "One taking advantage" , "Utiliser" , "Druggie" , "Person who takes drugs" .)