One jogging without a rest (9)
I believe the answer is:
remainder
'rest' is the definition.
(I know that rest can be written as remainder)
'one jogging without a' is the wordplay.
'one jogging' becomes 'reminder' (something which jogs one's memory).
'without' indicates putting letters inside ('without' can be similar in meaning to 'outside').
'reminder' enclosing 'a' is 'REMAINDER'.
(Other definitions for remainder that I've seen before include "book going cheap" , "Sell off book stock cheaply" , "The part that is left over" , "that's left" , "set of unsold books" .)