Terse conservative in US city in charge (7)
I believe the answer is:
laconic
'terse' is the definition.
('laconic' can be a synonym of 'terse')
'conservative in us city in charge' is the wordplay.
'conservative' becomes 'con' (I've seen this in other clues).
'in' indicates putting letters inside.
'us city' becomes 'la'.
'in charge' becomes 'ic'.
'la'+'ic'='laic'
'con' inserted inside 'laic' is 'LACONIC'.
(Other definitions for laconic that I've seen before include "Spartan" , "Terse, brief of speech" , "not saying much" , "Terse - can coil (anag)" , "Conical (anag) -- brief and to the point" .)