The most common and most likely answer to this crossword clue is the 6 letter word SMILEY
I've seen this crossword clue in The Guardian
S
M
I
L
E
Y
More clues leading to the result SMILEY
- Emoticon spy
- Sunny race in suburbs of Sydney
- I’m in agreement, being retired and over 50 :-)
- An icon of literary espionage?
- Spy master not really looking friendly
- Emoticon exposed my lies
- Harry Lime in shady case, grinning
- This emoticon was employed by the Circus, as mentioned in Tinker, Tailor, Soldier, Spy
Buddy explains!

The straight part
We know that "Sunny" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case sunny = smiley.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 SMILEY mean?
SMILEY noun- A simplified representation of a smiling face.
- A sequence of keyboard characters used to represent a happy mood, especially :) or :-) or other depiction of smiling.
- An improvised street weapon consisting of a length of chain with padlocks and other heavy objects affixed to one end.
- A roasted sheep's head.
- The type of piercing of the upper frenulum (upper lip).
- Cheerful and happy; smiling.
- Having one's throat slit from side to side.