The most common and most likely answer to this crossword clue is the 8 letter word AFFIANCE
I've seen this crossword clue in Financial Times
A
F
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More clues leading to the result AFFIANCE
Buddy explains!

The straight part
We know that "engaged" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case engaged = affiance.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does AFFIANCE mean?
AFFIANCE noun- Faith, trust.
- A solemn engagement, especially a pledge of marriage.
- To be betrothed to; to promise to marry.