Reason clock stops working in American's holidays (6,6)

I haven't cracked this one yet — but the brilliant team at Times for the Times have:

The cryptic intro got me to the answer. Although its meaning is self-explanatory I wouldn’t have considered ‘spring break’ as a lexical term, but my AI assistant now renamed Gemini advises: ‘Spring break’ in America is a time-honoured tradition for students, a week-long escape from classes and exams. It typically falls between March and April.