The most common and most likely answer to this crossword clue is the 6 letter word COGENT
I've seen this crossword clue in The Times
C
O
G
E
N
T
More clues leading to the result COGENT
- Powerfully persuasive company man
- Telling man to support firm
- Powerful dope hidden in bed
- Convincing chap to be prop for county
- Persuasive businessman
- Convincing businessman?
- Firm takes on man well-spoken and persuasive
- Strong man’s taken care of initially
- Company man is powerful
- Convincing over information produced in court
Buddy explains!

The straight part
We know that "Telling" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case telling = cogent.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 COGENT mean?
COGENT adjective- Reasonable and convincing; based on evidence.
- Appealing to the intellect or powers of reasoning.
- Forcefully persuasive; relevant, pertinent.