The most common and most likely answer to this crossword clue is the 9 letter word TWINKLING
I've seen this crossword clue in The Times
T
W
I
N
K
L
I
N
G
More clues leading to the result TWINKLING
- Second double fifty secured by man
- Second double fifty, man collects
- Mo initially treated with suspicion
- After Thailand fly over Kuala Lumpur in a flash
- Instant suspicion by these wives, initially
- Like a star that was initially faintest?
- Instant idea underlying the Web, primarily
- Like a star for a very short time
- Left enthralled by lookalike monarch for brief moment
- Bright tail of parrot fish catching glint
Buddy explains!

The straight part
We know that "Second" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case second = twinkling.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 TWINKLING mean?
TWINKLING verb- (of a source of light) to shine with a flickering light; to glimmer
- (chiefly of eyes) to be bright with delight
- To bat, blink or wink the eyes
- To flit to and fro
- Sparkling intermittently.
- A shining with fast intermittent light.
- A very short period, notionally the time it takes to blink the eyes.