City detective pursued by arsonists occasionally (7)
I believe the answer is:
detroit
'city' is the definition.
(Detroit is an example)
'detective pursued by arsonists occasionally' is the wordplay.
'detective' becomes 'det' (abbreviation for detective).
'pursued by' says to put letters next to each other.
'occasionally' indicates alternate letters.
The alternating letters of 'arsonists' are 'roit'.
'det'+'roit'='DETROIT'
(Other definitions for detroit that I've seen before include "U.S. city also known as Motown" , "US city in Michigan" , "Where cars are made" , "City in Michigan nicknamed Motown" , "US motor city" .)