Stole book in middle of excellent day (7)
I believe the answer is:
nobbled
'stole' is the definition.
(nobbling is a kind of stealing)
'book in middle of excellent day' is the wordplay.
'book' becomes 'b' (abbreviation for book).
'in middle of' means one lot of letters goes inside another.
'excellent' becomes 'noble' (I can't explain this - if you can you should give a lot more credence to this answer).
'day' becomes 'd' (abbreviation for day).
'b' put within 'noble' is 'nobble'.
'nobble'+'d'='NOBBLED'
Can you help me to learn more?
(Other definitions for nobbled that I've seen before include "Got at" , "Swindled" .)