The most common and most likely answer to this crossword clue is the 8 letter word UPGROWTH
U
P
G
R
O
W
T
H
More clues leading to the result UPGROWTH
Buddy explains!

The straight part
We know that "development" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case development = upgrowth.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 UPGROWTH mean?
UPGROWTH noun- The process or result of growing up; progress; development.