The most common and most likely answer to this crossword clue is the 10 plus 4 letter word ENGAGEMENT RING
I've seen this crossword clue in Independent
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More clues leading to the result ENGAGEMENT RING
- Sign union's promised to hire staff somewhere in Herts
- Mean ginger gent gets recycled present for his girlfriend
- Call after battle for sign of promise to unite
- English teacher wanting love wears attractive item of jewellery
- ,7 Union pledge to fight cartel
- Man of the match’s gift?
- Sign of commitment in battle arena
- Fight with cartel as indication of commitment to union
- Promising band put on prior to match
- Sign that wedding’s to be battle arena
Buddy explains!

The straight part
We know that "item of jewellery" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case item of jewellery = engagement ring.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.