The most common and most likely answer to this crossword clue is the 3 plus 4 letter word RAG DOLL
I've seen this crossword clue in The Times
R
A
G
D
O
L
L
More clues leading to the result RAG DOLL
- Paper taking party line repeatedly: child’s play
- Mock lines about the same toy
- Plaything bagged regularly in cylindrical pack
- Rex replaced old gal’s toy
- Make lines on paper that child can play with
- . African’s guide dog every so often left with large toy
- Toy dog lost during short mass meeting
- Beginning to regret everyone handling mangy dog’s toy
- Cat for newspaper girl, a cheap toy
- Toy dog lost during short march
Buddy explains!

The straight part
We know that "child’s play" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case child’s play = rag doll.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.