Jogger grabbing a rest (9)
I believe the answer is:
remainder
'rest' is the definition.
(I know that rest can be written as remainder)
'jogger grabbing a' is the wordplay.
'jogger' becomes 'reminder' (something which jogs one's memory).
'grabbing' is an insertion indicator.
'reminder' enclosing 'a' is 'REMAINDER'.
(Other definitions for remainder that I've seen before include "Rest - sell off (books) cheap" , "butt" , "It's left over after division" , "Leftovers" , "Unsold book; rest" .)