The most common and most likely answer to this crossword clue is the 4 plus 5 letter word LOST CAUSE
I've seen this crossword clue in The Daily Telegraph
L
O
S
T
C
A
U
S
E
More clues leading to the result LOST CAUSE
- See way, roughly, to exploit something hopeless
- Badly cooked cassoulet, one that can’t be saved
- . Spooner’s interpretation of penalty regulations in hopeless case
- Toss a clue around: no hope here
- Couldn’t find reason for failed campaign
- Despicable bloke trapping stray cats is a hopeless case
- Bewildered at clues, so struggle in vain
- Oral communication problem for crow with dead duck?
- Rephrases clauses to one without hope
- Cook cassoulet? It’s not worth the effort
Buddy explains!
The straight part
We know that "struggle in vain" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case struggle in vain = lost cause.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.