Large copy, mostly one for regular readers? (8)
I believe the answer is:
literati
'regular readers?' is the definition.
'large copy mostly one' is the wordplay.
'large' becomes 'l'.
'copy' becomes 'iterate'.
'mostly' means to remove the last letter.
'one' becomes 'i' (Roman numeral).
'iterate' with its last letter removed is 'iterat'.
'l'+'iterat'+'i'='LITERATI'
'for' acts as a link.
(Other definitions for literati that I've seen before include "Great minds" , "Bookish types" , "Well-read types" , "Learned, well-read people" , "The bookish intelligentsia" .)