Heartless theatrical princess keeps dictionary in school (7)
I believe the answer is:
roedean
'school' is the definition.
(I've seen this before)
'heartless theatrical princess keeps dictionary' is the wordplay.
'heartless theatrical princess' becomes 'rean' (I can't explain this - if you can you should believe this answer much more).
'keeps' is an insertion indicator (inserted letters are kept inside).
'dictionary' becomes 'OED' (Oxford English Dictionary).
'rean' going around 'oed' is 'ROEDEAN'.
'in' is the link.
Can you help me to learn more?
(Other definitions for roedean that I've seen before include "Brighton girls' school" , "Independent school" , "Girls public school" , "Famous girls' school" , "Posh girls' school in Sussex" .)