The most common and most likely answer to this crossword clue is the 7 letter word TWINKLE
I've seen this crossword clue in Financial Times
T
W
I
N
K
L
E
More clues leading to the result TWINKLE
- Wee nurses with gleam in eye
- Shine light, finally, on shellfish
- What stars do with wee curtains
- 1 12 character ignores Iggy — stars do it
- The instant wife puts ring on
- Call round with a wink
- Star does this act finally overcoming those picked out?
- Shine like the seafood in Yorkshire?
- Flash starter in tasty seafood
- Go around women for 11a
Buddy explains!

The straight part
We know that "The instant" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case the instant = twinkle.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 TWINKLE mean?
TWINKLE noun- A sparkle or glimmer of light
- A sparkle of delight in the eyes.
- A flitting movement
- A brief moment; a twinkling.
- The female genitalia.
- (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