The most common and most likely answer to this crossword clue is the 4 letter word TICS
T
I
C
S
More clues leading to the result TICS
Buddy explains!

The straight part
We know that "Habitual responses" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case habitual responses = tics.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 TICS mean?
TICS noun- A sudden, nonrhythmic motor movement or vocalization.
- (by extension) Something that is done or produced habitually or characteristically.
- (abbreviation) ticket