Flat racing here, short guy and small horse failing to finish (5)
I believe the answer is:
ripon
'flat racing here short' is the definition.
The definition suggests a singular noun which matches the answer.
'guy and small horse failing to finish' is the wordplay.
'guy' becomes 'ri' (I can't explain this - if you can you should believe this answer much more).
'and' is a charade indicator (letters next to each other).
'small horse' becomes 'pony' (I've seen this in another clue).
'failing to finish' means to remove the last letter.
'pony' with its final letter removed is 'pon'.
'ri'+'pon'='RIPON'
Can you help me to learn more?
(Other definitions for ripon that I've seen before include "Yorkshire city with cathedral and racecourse" , "historic city" , "see" , "N. Yorks market town" , "minster" .)