The most common and most likely answer to this crossword clue is the 8 letter word SUSPENSE
I've seen this crossword clue in The Daily Telegraph
S
U
S
P
E
N
S
E
More clues leading to the result SUSPENSE
- Excitement as American writers visit southeast
- Such an account makes one nervous?
- Soups regularly served with neeps, mashed in anticipation
- Cliffhanging sort of account?
- . Doubt South American writer’s on ecstasy
- American poet almost captures state of uncertainty
- Uncertainty of distinguishing feature in meaning
- South American writers echo doubt
- Anticipation of wisdom keeping us quiet
- Feeling about American power: nervous uncertainty
Buddy explains!

The straight part
We know that "tension" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case tension = suspense.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 SUSPENSE mean?
SUSPENSE noun- The condition of being suspended; cessation for a time.
- The pleasurable emotion of anticipation and excitement regarding the outcome or climax of a book, film etc.
- The unpleasant emotion of anxiety or apprehension in an uncertain situation.
- A temporary cessation of one's right; suspension, as when the rent or other profits of land cease by unity of possession of land and rent.
- Held or lifted up; held or prevented from proceeding.
- Expressing, or proceeding from, suspense or doubt.