Short Persian jockeys have ambition (6)
I believe the answer is:
aspire
'have ambition' is the definition.
(I've seen this before)
'short persian jockeys' is the wordplay.
'short' means to remove the last letter.
'jockeys' indicates anagramming the letters.
'persian' with its final letter removed is 'persia'.
'persia' is an anagram of 'ASPIRE'.
(Other definitions for aspire that I've seen before include "Hanker" , "Direct one's hopes and ambitions" , "Wish to rise (to)" , "Have hopes (to achieve something)" , "Set your sights on" .)