The most common and most likely answer to this crossword clue is the 6 letter word BROODS
I've seen this crossword clue in The Daily Telegraph
B
R
O
O
D
S
Buddy explains!
The straight part
We know that "groups of children" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case groups of children = broods.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 BROODS mean?
BROODS noun- The young of certain animals, especially a group of young birds or fowl hatched at one time by the same mother.
- The young of any egg-laying creature, especially if produced at the same time.
- The eggs and larvae of social insects such as bees, ants and some wasps, especially when gathered together in special brood chambers or combs within the colony.
- The children in one family; offspring.
- That which is bred or produced; breed; species.
- Parentage.
- Heavy waste in tin and copper ores.
- To keep an egg warm to make it hatch.
- To protect (something that is gradually maturing); to foster.
- (typically with about or over) To dwell upon moodily and at length, mainly alone.
- To be bred.