Row holding up extremely busy author’s identification (2-4)
I believe the answer is:
by-line
'author's identification' is the definition.
The definition and answer can be both acts as well as being singular nouns.
Maybe you can see an association between them that I don't see?
'row holding up extremely busy' is the wordplay.
'row' becomes 'line' (as in a row of things).
'holding up' is a charade indicator (letters next to each other) (in a down clue, some letters go below others).
'extremely' suggests removing the centre (only the extremes of the word are used).
'busy' with its centre removed is 'by'.
'line' after 'by' is 'BY-LINE'.
Can you help me to learn more?
(Other definitions for by-line that I've seen before include "Newspaper column by named writer" , "Author's credit in paper" , "Newspaper article naming the writer" , "It gives the name of the writer of a report" , "It gives the name of the writer of an article" .)