Jogger carrying a cut-price book (9)
I believe the answer is:
remainder
'cut-price book' is the definition.
'remainder' can be an answer for 'book' (I've seen this before). I'm not certain of the 'cut-price' bit.
'jogger carrying a' is the wordplay.
'jogger' becomes 'reminder' (something which jogs one's memory).
'carrying' is an insertion indicator.
'reminder' enclosing 'a' is 'REMAINDER'.
Can you help me to learn more?
(Other definitions for remainder that I've seen before include "Dispose of unsold books cheaply" , "deposit" , "It's left over after division" , "part that is still to come" , "Unsold book; rest" .)