British novel that's about English rock (4,5)
I believe the answer is:
bath stone
'rock' is the definition.
(type of stone found near Bath)
'british novel that's about english' is the wordplay.
'british' becomes 'b' (abbreviation e.g. in 'BBC').
'novel' indicates anagramming the letters (letters in a new or novel order).
'about' becomes 'on' (as in a book 'on' a certain topic).
'english' becomes 'e' (abbreviation).
'thats' is an anagram of 'athst'.
'b'+'athst'+'on'+'e'='BATH STONE'
(Other definitions for bath stone that I've seen before include "Possible material for sculptor" , "pumice?" .)