The most common and most likely answer to this crossword clue is the 10 letter word ALTERNATES
I've seen this crossword clue in Financial Times
A
L
T
E
R
N
A
T
E
S
Buddy explains!
The straight part
We know that "Acts in sequence" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case acts in sequence = alternates.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 ALTERNATES mean?
ALTERNATES noun- That which alternates with something else; vicissitude.
- A substitute; an alternative; one designated to take the place of another, if necessary, in performing some duty.
- A proportion derived from another proportion by interchanging the means.
- A replacement of equal or greater value or function.
- Figures or tinctures that succeed each other by turns.
- To perform by turns, or in succession; to cause to succeed by turns; to interchange regularly.
- To happen, succeed, or act by turns; to follow reciprocally in place or time; followed by with.
- To vary by turns.
- To perform an alternation (removal of alternate vertices) on (a polytope or tessellation); to remove vertices (from a face or edge) as part of an alternation.