Small computer at work on this? (8)

I believe the answer is:
tabletop
'this?' is the definition.
The definition suggests a singular noun which matches the answer.
'small computer at work' is the wordplay.
'small computer' becomes 'tablet' (I've seen this before).
'at' is a charade indicator (letters next to each other).
'work' becomes 'op' (short for opus).
'tablet'+'op'='TABLETOP'
'on' is the link.
Can you help me to learn more?
(Other definitions for tabletop that I've seen before include "Work or eating surface" , "Flat surface for working or dining" , "where food is usually served" , "Flat domestic surface" .)
