Difficult book about Russian money (11)
I believe the answer is:
troublesome
'difficult' is the definition.
(similar in meaning)
'book about russian money' is the wordplay.
'book' becomes 'tome' (a tome is a book).
'about' means one lot of letters goes inside another.
'russian money' becomes 'roubles' (I've seen this before).
'tome' placed around 'roubles' is 'TROUBLESOME'.
(Other definitions for troublesome that I've seen before include "Causing difficulty" , "Trying" , "problematic" , "Mischievous - vexatious" , "Difficult" .)