Small book producer, one doing a run (8)
I believe the answer is:
sprinter
'small book producer one doing a run' is the definition.
I can't tell whether this defines the answer.
'small book producer one doing a run' is the wordplay.
I cannot quite see how this works, but
'small' could be 's' (abbreviation - e.g. clothes size) and 's' is found within the answer.
'book' could be 'nt' (I've seen this in other clues) and 'nt' is found in the answer.
'one' could be 'i' (Roman numeral) and 'i' is located in the answer.
'run' could be 'r' (cricket abbreviation) and 'r' is present in the answer.
'a' could be 'per' and 'per' is present in the leftover letters.
No letters remain.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for sprinter that I've seen before include "Usain Bolt, for instance" , "One moves quickly" , "Fast runner" , "one promising a fast run?" , "one running" .)