The most common and most likely answer to this crossword clue is the 12 letter word UNSEASONABLE
I've seen this crossword clue in The Guardian
U
N
S
E
A
S
O
N
A
B
L
E
Buddy explains!
The straight part
We know that "not fitting for the time of year" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case not fitting for the time of year = unseasonable.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 UNSEASONABLE mean?
UNSEASONABLE adjective- Not in accordance with the season.