Monarchs maybe checked on board (5)
I believe the answer is:
kings
'monarchs' is the definition.
(king is a kind of monarch)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for kings that I've seen before include "two books in > a number of colleges" , "Monarchs" , "a couple of books" , "Not subjects among those" , "Henry James, or Edward Lear?" .)