The most common and most likely answer to this crossword clue is the 7 letter word CORONET
I've seen this crossword clue in Independent
C
O
R
O
N
E
T
More clues leading to the result CORONET
- Small crown, gold one seen in court
- Goodness! Note damaged headdress
- My one-time mark of noble rank?
- In court, non-U individual displaying small crown
- My single bit of trivia: the knob on a deer’s antler is a crown
- . Golden one may be seen in Court?
- 26 has one county singer sent up
- Piece of brass enclosing ring that’s worn by noble
- Musical instrument contains nothing of use to lesser royalty
- Regal item soldiers put on individual in court
Buddy explains!

The straight part
We know that "the knob on a deer’s antler/crown" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case the knob on a deer’s antler/crown = coronet.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 CORONET mean?
CORONET noun- A small crown, such as is worn by a noble.
- The ring of tissue between a horse's hoof and its leg.
- The traditional lowest regular commissioned officer rank in the cavalry.
- Any of several hummingbirds in the genus Boissonneaua.
- A species of moth, Craniophora ligustri.