From the monarch, a sign of willingness (5)
I believe the answer is:
offer
'a sign of willingness' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
'from the monarch' is the wordplay.
'from' becomes 'off' (eg someone might be from or 'off' a TV show).
'the monarch' becomes 'ER' (abbreviation for Elizabeth Regina, British Queen).
'off'+'er'='OFFER'
Can you help me to learn more?
(Other definitions for offer that I've seen before include "Volunteer, present" , "Present to or make a bid" , "Tender or propose" , "Volunteer -- proposal" , "killer?" .)