The most common and most likely answer to this crossword clue is the 6 letter word SLEEPY
I've seen this crossword clue in Financial Times
S
L
E
E
P
Y
More clues leading to the result SLEEPY
- Drowsy agent outside shelter
- Dozy agent surrounding sheltered area
- Tired agent outside shelter
- Quiet spot round sheltered side
- Agent keeping out of the wind, far from alert
- Agent keeping general quiet
- Sheltered area is covered by agent not fully alert
- Agent, having secured shelter, ready to go out?
- Small miner strips vertical end of quarry
- Tired MI6 man devouring fish on way back
Buddy explains!

The straight part
We know that "Tired" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case tired = sleepy.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 SLEEPY mean?
SLEEPY noun- The gum that builds up in the eye; sleep, gound.
- Tired; feeling the need for sleep.
- Suggesting tiredness.
- Tending to induce sleep; soporific.
- Dull; lazy; heavy; sluggish.
- Quiet; without bustle or activity.