The most common and most likely answer to this crossword clue is the 7 letter word TELLING
I've seen this crossword clue in Independent
T
E
L
L
I
N
G
More clues leading to the result TELLING
- Convincing action of informer?
- Significant narration
- Significant relation
- Substantial bidding
- Reprimand tons with cheap disposal not having succeeded
- Significant skill of narrator?
- . Relation of Swiss folk hero in German capital
- Significant disclosure
- Significant to find Swiss nationalist in government
- Narration is effective
Buddy explains!

The straight part
We know that "Significant" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case significant = telling.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 TELLING mean?
TELLING verb- (archaic outside of idioms) To count, reckon, or enumerate.
- To narrate.
- To convey by speech; to say.
- To instruct or inform.
- To order; to direct, to say to someone.
- To discern, notice, identify or distinguish.
- To reveal.
- To be revealed.
- To have an effect, especially a noticeable one; to be apparent, to be demonstrated.
- To use (beads or similar objects) as an aid to prayer.
- To inform someone in authority about a wrongdoing.
- (authorship) To reveal information in prose through outright expository statement -- contrasted with show
- Having force, or having a marked effect; weighty, effective.
- Revealing information; bearing significance.
- Serving to convince.
- The act of narration.
- The disclosure of information.
- Counting, numbering.
- (usually in the negative) Ability to determine.