The most common and most likely answer to this crossword clue is the 4 letter word ILLS
I've seen this crossword clue in The Daily Telegraph
I
L
L
S
More clues leading to the result ILLS
- Invoices not faced become big problems
- Still sick, accepting these?
- Evils of factories lacking male leadership
- Health problems as medication’s losing initial power
- Not leader: Clinton’s misfortunes
- Head off demands for money, they’re troublesome
- Schools doctor withdrawing complaints
- Ailments needing tablets, relieving the head
- Troubles with ledge beginning to fall down
- Evils of liberal left infiltrating Iceland
Buddy explains!

The straight part
We know that "Troubles" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case troubles = ills.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 ILLS mean?
ILLS noun- (often pluralized) Trouble; distress; misfortune; adversity.
- Harm or injury.
- Evil; moral wrongfulness.
- A physical ailment; an illness.
- PCP, phencyclidine.