Tiny writing on an excellent etching (4,5)
I believe the answer is:
fine print
'tiny writing' is the definition.
The definition suggests a singular noun which matches the answer.
'on an excellent etching' is the wordplay.
'on' says to put letters next to each other.
'an excellent' becomes 'fine' (I've seen this in another clue).
'etching' becomes 'print' (I can't explain this - if you can you should believe this answer much more).
'fine' put next to 'print' is 'FINE PRINT'.
Can you help me to learn more?
(Other definitions for fine print that I've seen before include "details of policy" , "which one should look for before signing" .)