It may be topped with a computer (4)
I believe the answer is:
desk
This clue might be a double definition.
'it may be topped' is the first definition.
The definition suggests a singular noun which matches the answer.
'computer' is the second definition.
The definition and answer can be both man-made objects as well as being singular nouns.
Maybe there's an association between them I don't understand?
'with a' is the link.
Can you help me to learn more?
(Other definitions for desk that I've seen before include "Table for writing, reading etc" , "Writer's workbench" , "Place for writing or serving the public" , "Bureau" , "Secretaire" .)