The most common and most likely answer to this crossword clue is the 7 letter word WITCHES
I've seen this crossword clue in The Guardian
W
I
T
C
H
E
S
More clues leading to the result WITCHES
- Crones change direction from head to foot
- Weird sisters pollarding birches, say
- Contest for mate between salt and seaman on tub in latenight meeting
- As well as bagging game, sailor attends club for midnight meeting
- Fascinating women with desires
- They may produce a spell of levity before the game, cutting Spurs’ lead
Buddy explains!

The straight part
We know that "Weird sisters" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case weird sisters = witches.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 WITCHES mean?
WITCHES noun- A person who practices witchcraft; a woman or man who practices witchcraft.
- An ugly or unpleasant woman.
- One who exercises more-than-common power of attraction; a charming or bewitching person.
- One given to mischief, especially a woman or child.
- A certain curve of the third order, described by Maria Agnesi under the name versiera.
- The stormy petrel.
- Any of a number of flatfish:
- The Indomalayan butterfly Araotes lapithis, of the family Lycaenidae.
- To practise witchcraft.
- To bewitch.
- To dowse for water.
- A cone of paper which is placed in a vessel of lard or other fat and used as a taper.