Sense city in need of development -- that's a must (9)
I believe the answer is:
necessity
'a must' is the definition.
(thesaurus)
'sense city in need of development' is the wordplay.
'sense city' anagrams to 'NECESSITY'.
Though, I'm not clear how this is indicated.
'that's' acts as a link.
Can you help me to learn more?
(Other definitions for necessity that I've seen before include "Fundamental" , "Something essential or indispensable" , "It's said to be the mother of invention" , "Prerequisite - poverty" , "Need, exigency" .)