The most common and most likely answer to this crossword clue is the 6 letter word COLDER
I've seen this crossword clue in The Guardian
C
O
L
D
E
R
More clues leading to the result COLDER
Buddy explains!
The straight part
We know that "not so friendly" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case not so friendly = colder.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 COLDER mean?
COLDER adjective- (of a thing) Having a low temperature.
- (of the weather) Causing the air to be cold.
- (of a person or animal) Feeling the sensation of coldness, especially to the point of discomfort.
- Unfriendly, emotionally distant or unfeeling.
- Dispassionate, not prejudiced or partisan, impartial.
- Completely unprepared; without introduction.
- Unconscious or deeply asleep; deprived of the metaphorical heat associated with life or consciousness.
- (usually with "have" or "know" transitively) Perfectly, exactly, completely; by heart.
- (usually with "have" transitively) Cornered, done for.
- Not pungent or acrid.
- Unexciting; dull; uninteresting.
- Affecting the sense of smell (as of hunting dogs) only feebly; having lost its odour.
- Not sensitive; not acute.
- Distant; said, in the game of hunting for some object, of a seeker remote from the thing concealed. Compare warm and hot.
- Having a bluish effect; not warm in colour.
- Rarely used or accessed, and thus able to be relegated to slower storage.
- Without compassion; heartless; ruthless