The most common and most likely answer to this crossword clue is the 4 letter word TOGA
I've seen this crossword clue in The Daily Telegraph
T
O
G
A
More clues leading to the result TOGA
- Singular item of clothing linked to ancients principally
- Cheers about error from defence giving cover for Caesar
- Old garment, article obtained in recession
- Roman garment of past time on the way back
- Got up, put on a white robe
- One-piece garment not new in Friendly Islands
- Understood reversed article to be ancient dress
- Apparently single item of clothing – a Roman one
- Singular clothing article
- Turn up wearing reservists’ old clothing
Buddy explains!

The straight part
We know that "Type of garment, ancient primarily" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case type of garment, ancient primarily = toga.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 TOGA mean?
TOGA noun- A loose outer garment worn by the citizens of Ancient Rome.
- A loose wrap gown.
- An academic gown.