The most common and most likely answer to this crossword clue is the 6 letter word DAFTER
I've seen this crossword clue in The Daily Telegraph
D
A
F
T
E
R
More clues leading to the result DAFTER
Buddy explains!

The straight part
We know that "being less sensible" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case being less sensible = dafter.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 DAFTER mean?
DAFTER adjective- Foolish, silly, stupid.
- Crazy, insane, mad.
- Gentle, meek, mild.
- One’s female offspring.
- A female descendant.
- A daughter language.
- A nuclide left over from radioactive decay.
- (of a parse tree) A descendant.
- (by extension) A female character of a creator.