Fabulous runner caught napping in race (4)
I believe the answer is:
hare
'napping in race' is the definition.
'hare' can be an answer for 'race' (hare can mean to run fast). I am not sure about the 'napping in' bit.
'fabulous runner caught' is the wordplay.
'fabulous' becomes 'h' (I am not sure about this - if you are sure you should believe this answer much more).
'runner' becomes 'r' (abbreviation for river).
'caught' shows a homophone (sound like) (heard).
'r' sounds like 'are'.
'h'+'are'='HARE'
Can you help me to learn more?
(Other definitions for hare that I've seen before include "Fast-running mammal" , "'Swift, long-eared animal (4)'" , "'You can't run with the . . . . and hunt with the hounds'" , "Rabbit-like creature" , "animal running in fields" .)