Thoroughbred irritated over what it's carrying (5)
I believe the answer is:
rider
'over what it's carrying' is the definition.
I can't tell whether this definition defines the answer.
'thoroughbred irritated' is the wordplay.
'RIDER' is hidden backwards within the letters.
However, I am not sure how this is indicated.
Can you help me to learn more?
(Other definitions for rider that I've seen before include "Jockey" , "Horseman or supplementary jury verdict" , "Addition to verdict" , "Condition added to a legislative bill" , "Revere, for example" .)