Ancient writer understood Guardian readers (7)
I believe the answer is:
tacitus
'ancient writer' is the definition.
'tacitus' can be an answer for 'writer' (I've seen this before). I'm unsure of the 'ancient' bit.
'understood guardian readers' is the wordplay.
I cannot really understand how this works, but
'understood' could be 'tacit' (I've seen this in another clue) and 'tacit' is found within the answer.
'guardian' could be 'us' (the crossword setter and their Guardian colleagues) and 'us' is found within the answer.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for tacitus that I've seen before include "Roman politician and historian" , "Old history master" , "Roman historian, annalist" , "Old historian" , "Writer" .)