The most common and most likely answer to this crossword clue is the 6 letter word SADDER
I've seen this crossword clue in The Guardian
S
A
D
D
E
R
More clues leading to the result SADDER
- Second snake further down
- More blue snakes bottom up
- Second summer extra-blue?
- Dreads becoming even more unhappy
- Snake is under bottom of leaves, further down
- More blue markings at the bottom on reptile
- Small venomous creature making one less carefree
- Small snake is comparatively low
- Son meeting snake is not so happy
- Second snake is further down
Buddy explains!

The straight part
We know that "even more unhappy" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case even more unhappy = sadder.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 SADDER mean?
SADDER adjective- (heading) Emotionally negative.
- Sated, having had one's fill; satisfied, weary.
- Steadfast, valiant.
- Dignified, serious, grave.
- Naughty; troublesome; wicked.
- Unfashionable; socially inadequate or undesirable.
- Soggy (to refer to pastries).
- Heavy; weighty; ponderous; close; hard.