The most common and most likely answer to this crossword clue is the 6 letter word SERENE
I've seen this crossword clue in Financial Times
S
E
R
E
N
E
More clues leading to the result SERENE
- Calm observed around queen, note
- Composed, having dry quarters
- Calm observed round River Ribble finally
- Collected baked noodles and egg starters
- Poise renewed, in part unruffled
- Calm song after sunset needing publicity
- Calm sneer upset English
- Unruffled by prophet in conversation about space
- Tranquil piece of music a duke brought out
- Bishop’s jurisdiction keeps soldiers’ quarter peaceful
Buddy explains!

The straight part
We know that "Collected" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case collected = serene.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 SERENE mean?
SERENE noun- Serenity; clearness; calmness.
- Evening air; night chill.
- To make serene.
- Peaceful, calm, unruffled.
- Without worry or anxiety; unaffected by disturbance.
- Fair and unclouded (as of the sky); clear; unobscured.
- Used as part of certain titles, originally to indicate sovereignty or independence.
- A fine rain from a cloudless sky after sunset.