Worried by San Diego riots (8)
I believe the answer is:
agonised
'worried' is the definition.
(I've seen this before)
'by san diego riots' is the wordplay.
'by' says to put letters next to each other.
'riots' is an anagram indicator.
'san' put after 'diego' is 'diegosan'.
'diegosan' anagrammed gives 'AGONISED'.
(Other definitions for agonised that I've seen before include "Tormented" , "Felt mental anguish (over a decision)" , "San Diego (anagram)" , "Diagnose (anag)" , "Was in great doubt" .)