Agree to accept 'Leave' with difficulty (10)
I believe the answer is:
complexity
'difficulty' is the definition.
(thesaurus)
'agree to accept leave with' is the wordplay.
'agree' becomes 'comply' (complying is a kind of agreeing).
'to accept' means one lot of letters goes inside another.
'leave with' becomes 'exit' ('exit' can be a synonym of 'leave'. I am not sure about the 'with' bit.**).
'comply' going around 'exit' is 'COMPLEXITY'.
Can you help me to learn more?
(Other definitions for complexity that I've seen before include "It's far from straightforward" , "intricate quality" , "elaborate" , "Intricacy" , "Involvement" .)