City deal involved assistant (8)
I believe the answer is:
adelaide
'city' is the definition.
(Adelaide is an example)
'deal involved assistant' is the wordplay.
'involved' is an anagram indicator (involved can mean confusing or complex).
'assistant' becomes 'aide' (aide is a kind of assistant).
'deal' with letters rearranged gives 'adel'.
'adel'+'aide'='ADELAIDE'
(Other definitions for adelaide that I've seen before include "Antipodean city" , "Girl" , "town" , "Lead aide to Oz" , "Commonwealth city" .)