The most common and most likely answer to this crossword clue is the 5 letter word MORSE
M
O
R
S
E
More clues leading to the result MORSE
- American inventor leaving small item unfinished
- Telegraph characters sent over in Times Roman
- Love once forsworn by sullen sleuth
- & 23dn. Cry for help expressed in this version of some credo?
- Inventor showing regret when putting off engineers
- & 24 Flashy system buggered up some credo?
- Means of communication with a walrus?
- Somewhat dotty detective?
- TV detective a bit short
- Detective with feeling of contrition about to be let off
Buddy explains!

The straight part
We know that "cry for help (i.e. SOS, can be) expressed in this" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case cry for help (i.e. sos, can be) expressed in this = morse.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 MORSE mean?
MORSE noun- A clasp or fastening used to fasten a cope in the front, usually decorative.
- A walrus.