The most common and most likely answer to this crossword clue is the 6 letter word HIDDEN
H
I
D
D
E
N
More clues leading to the result HIDDEN
- Oh, I’d deny penning this type of clue
- Obscure female, one with two daughters to accommodate
- Girl keeping identification card ultimately concealed
- Cryptic crossword finally found in papers taken by woman
- Party girl keeping one large chest measurement under wraps
- Ambassador carries identification with duke’s name concealed
- Secret greeting before daughter is taken into private room
- Hard to put a name to home that’s not obvious
- Secret I’d discovered initially guarded by female
- Concealed layer swallows did for building
Buddy explains!

The straight part
We know that "Secret" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case secret = hidden.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 HIDDEN mean?
HIDDEN adjective- Located or positioned out of sight; not visually apparent.
- Obscure.
- To put (something) in a place where it will be harder to discover or out of sight.
- To put oneself in a place where one will be harder to find or out of sight.