The most common and most likely answer to this crossword clue is the 8 letter word TEARIEST
I've seen this crossword clue in Financial Times
T
E
A
R
I
E
S
T
More clues leading to the result TEARIEST
Buddy explains!
The straight part
We know that "looking most unhappy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case looking most unhappy = teariest.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 TEARIEST mean?
TEARIEST adjective- Of a person, having eyes filled with tears; inclined to cry.
- Of eyes, filled with tears.