The most common and most likely answer to this crossword clue is the 6 letter word SIGNAL
I've seen this crossword clue in Financial Times
S
I
G
N
A
L
More clues leading to the result SIGNAL
- Noteworthy contributor to rail safety
- Remarkable note penned by prisoner is handed over
- Indication good in snail after treatment
- Remarkable gesture
- Remarkable gesture
- Big loans arranged by on-line control centre
- Remarkable old film director is making a comeback
- Perhaps Leo and Al will send a message
- Aligns malfunctioning warning light
- Token is returned by gutted Glaswegian gangster
Buddy explains!

The straight part
We know that "Remarkable" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case remarkable = signal.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 SIGNAL mean?
SIGNAL noun- A sequence of states representing an encoded message in a communication channel.
- Any variation of a quantity or change in an entity over time that conveys information upon detection.
- A sign made to give notice of some occurrence, command, or danger, or to indicate the start of a concerted action.
- An on-off light, semaphore, or other device used to give an indication to another person.
- (of a radio, TV, telephone, internet, etc.) An electromagnetic action, normally a voltage that is a function of time, that conveys the information of the radio or TV program or of communication with another party.
- An action, change or process done to convey information and thus reduce uncertainty.
- A token; an indication; a foreshadowing; a sign.
- Useful information, as opposed to noise.
- A simple interprocess communication used to notify a process or thread of an occurrence.
- A signalling interaction between cells
- To indicate; to convey or communicate by a signal.
- To communicate with (a person or system) by a signal.
- Standing above others in rank, importance, or achievement.