Lots written about large kingdoms (6)
I believe the answer is:
realms
'kingdoms' is the definition.
(I've seen this before)
'lots written about large' is the wordplay.
'lots' becomes 'reams' (I have seen 'Lots of paper ' mean 'reams' so perhaps 'lots' could also mean 'reams').
'written about' means one lot of letters goes inside another.
'large' becomes 'l'.
'reams' going around 'l' is 'REALMS'.
(Other definitions for realms that I've seen before include "areas of interest" , "Fields of activity or interest - sound monarchical" , "Kingdoms, or fields of interest" , "Kingdoms, domains" , "regions" .)