The most common and most likely answer to this crossword clue is the 6 letter word SIGHED
I've seen this crossword clue in The Guardian
S
I
G
H
E
D
Buddy explains!
The straight part
We know that "expressed sadness" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case expressed sadness = sighed.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 SIGHED mean?
SIGHED verb- To inhale a larger quantity of air than usual, and immediately expel it; to make a deep single audible respiration, especially as the result or involuntary expression of fatigue, exhaustion, grief, sorrow, frustration, or the like.
- To lament; to grieve.
- To utter sighs over; to lament or mourn over.
- To experience an emotion associated with sighing.
- To make a sound like sighing.
- To exhale (the breath) in sighs.
- To express by sighs; to utter in or with sighs.