The most common and most likely answer to this crossword clue is the 8 letter word HEADGEAR
I've seen this crossword clue in Independent
H
E
A
D
G
E
A
R
More clues leading to the result HEADGEAR
- Try introducing skinned badger hats
- Be told about saw cutting out a hat
- One evasive about articles separately depicting milliner’s products?
- Top property Balmoral perhaps
- Nightcap, perhaps, for acid-user anticipating stash of drugs
- Equipment needed by top bowlers for instance
- Perhaps boater’s cape beginning to get attention
- 27 agreed about carrying a hat?
- Guard a king carrying a crown, say
- Principal effects of nightcap?
Buddy explains!

The straight part
We know that "nightcap" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case nightcap = headgear.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 HEADGEAR mean?
HEADGEAR noun- Anything worn on the head, such as a helmet.
- The harness that fits on a horse's head.
- The lifting gear at the head of a mine or deep well.
- The rigging on the foresail
- A type of orthodontic appliance attached to dental braces that aids in correcting severe bite problems.