The most common and most likely answer to this crossword clue is the 2 plus 5 letter word NO ENTRY
N
O
E
N
T
R
Y
More clues leading to the result NO ENTRY
- Sign of gas returning? Have to go!
- New leader, new Tory takes measure: Exit only?
- Unsuccessful competitor’s situation, perhaps way to go ahead is barred
- Sign of an unsuccessful solver?
- Attempt to follow reflective fluorescent road sign
- None could go beyond this sign
- d TMO’s ruling nut has punched and passage denied
Buddy explains!

The straight part
We know that "sign" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sign = no entry.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.