The most common and most likely answer to this crossword clue is the 8 letter word BROTHERS
I've seen this crossword clue in Financial Times
B
R
O
T
H
E
R
S
More clues leading to the result BROTHERS
- Members of union run into worries
- Queen entering worries members of the family
- Some religious worries overwhelming rector finally
- Monks regularly defrost soup in advance
- Fusses about end of Labour’s Ed and David?
- Relatives who join a religious order
- Makes an effort to cross river for comrades
- Fusses about Royal relatives
- Marx perhaps worries about Right
- For example, Marx family members as comrades
Buddy explains!

The straight part
We know that "Marx perhaps" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case marx perhaps = brothers.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 BROTHERS mean?
BROTHERS noun- Son of the same parents as another person.
- A male having at least one parent in common with another (see half-brother, stepbrother).
- A male fellow member of a religious community, church, trades union etc.
- A form of address to a man.
- A black male.
- Somebody, usually male, connected by a common cause or situation.
- Someone who is a peer, whether male or female.
- To treat as a brother.