Exercises adopted by licentious escorts (4)
I believe the answer is:
uses
'exercises' is the definition.
(to exercise something can mean to use it)
'adopted by licentious escorts' is the wordplay.
'adopted by' says the answer is hidden in the clue.
'USES' is hidden in the letters of 'licentious escorts'.
(Other definitions for uses that I've seen before include "manipulates" , "Utilises" , "Puts into service" , "Operates" , "Consumes; treats" .)