Shabby Italian rider's content to go up bridle path (6,3)
I believe the answer is:
rotten row
'bridle path' is the definition.
(bridal path in London)
'shabby italian rider's content to go up' is the wordplay.
'shabby' becomes 'worn' (similar in meaning).
'italian rider' becomes 'Dettori' (jockey Frankie Dettori).
'content' means to look at the middle letters.
'to go up' shows that the letters should be reversed in order (I've seen 'goes up' mean this).
The centre of 'dettori' is 'ettor'.
'worn'+'ettor'='wornettor'
'wornettor' in reverse letter order is 'ROTTEN ROW'.
(Other definitions for rotten row that I've seen before include "Capital place for riding" , "Bridleway in Hyde Park" , "comes to an end at Hyde Park Corner" , "Where to see riders" , "Once fashionable avenue for riders in London" .)