The most common and most likely answer to this crossword clue is the 6 letter word ENAMEL
I've seen this crossword clue in The Times
E
N
A
M
E
L
More clues leading to the result ENAMEL
- Term the Spanish put about for glossy coating
- English word for something initially like paint
- Nail polish back in style, man explains
- Bloke entering shelter returned protective coat
- In middle of facelift, call for the hard stuff
- English reputation lies initially in painted artwork
- Title accepted by the Spanish Crown Protector
- . Paint coat of eggshell around handle
- Gloss over title claimed by the Spanish
- Call into East London, primarily for some hard stuff
Buddy explains!

The straight part
We know that "Crown Protector" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case crown protector = enamel.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 ENAMEL mean?
ENAMEL noun- An opaque, glassy coating baked onto metal or ceramic objects.
- A coating that dries to a hard, glossy finish.
- The hard covering on the exposed part of a tooth.
- A cosmetic intended to give the appearance of a smooth and beautiful complexion.
- To coat or decorate with enamel.
- To variegate with colours, as if with enamel.
- To form a glossy surface like enamel upon.
- To disguise with cosmetics, as a woman's complexion.