Promise to marry criminal at brothel (9)

I believe the answer is:

betrothal

I'm a little stuck... Click here to teach me more about this clue!

'promise' is the definition.
(I know that betrothal is a type of promise)

'criminal at brothel' is the wordplay.
'criminal' is an anagram indicator.
'at'+'brothel'='atbrothel'
'atbrothel' is an anagram of 'BETROTHAL'.

'to marry' acts as a link.
This may not be right. Some or all of it may belong to another bit of the clue.

Can you help me to learn more?

(Other definitions for betrothal that I've seen before include "Engagement to marry" , "Commitment" , "Plight" , "Promise of marriage" , "Pledge" .)

I've seen this clue in The Independent.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.