The words in bold (When Shawn arrives at work) represent a dependent clause.
From questions similar to yours, you can see that the clause "When Shawn arrives at work" is the part marked in bold.
These words represent a dependent clause, since reading it does not allow the reader to understand its meaning and purpose, requiring a complement to be added.
You can learn more about dependent clauses at the link:
https://brainly.com/question/27346514