The most common and most likely answer to this crossword clue is the 9 letter word OVERCROWD
I've seen this crossword clue in The Daily Telegraph
O
V
E
R
C
R
O
W
D
More clues leading to the result OVERCROWD
Buddy explains!
The straight part
We know that "put in too many" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case put in too many = overcrowd.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 OVERCROWD mean?
OVERCROWD verb- To fill beyond reasonable limits, with people, animals, objects or information.