The most common and most likely answer to this crossword clue is the 7 letter word LITTLER
I've seen this crossword clue in The Guardian
L
I
T
T
L
E
R
Buddy explains!
The straight part
We know that "not so developed" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case not so developed = littler.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 LITTLER mean?
LITTLER adjective- Small in size.
- Insignificant, trivial.
- Very young.
- (of a sibling) Younger.
- (also Little) Used with the name of a place, especially of a country or its capital, to denote a neighborhood whose residents or storekeepers are from that place.
- Small in amount or number, having few members.
- Short in duration; brief.
- Small in extent of views or sympathies; narrow; shallow; contracted; mean; illiberal; ungenerous.