One of those on The Screen from Rising, Revenue Commissioners and old police force (6)
I believe the answer is:
cursor
'one' is the definition.
Although both the answer and definition are singular nouns, I can't understand how they can define each other.
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for cursor that I've seen before include "Indicator on a visual display" , "Place-marker on screen" , "Kind of pointer on computer screen" , "Computer screen marker" , "Indicator on computer monitor" .)