Mission in Kampala modest (5)
I believe the answer is:
alamo
'mission' is the definition.
(famous mission and siege from the Texas revolution)
'in kampala modest' is the wordplay.
'in' says the answer is hidden in the clue.
'ALAMO' can be found hidden inside 'kampala modest'.
(Other definitions for alamo that I've seen before include "US mission" , "Site of a Texas siege, 1836" , "The --, Texan mission besieged in 1836" , "Texas mission taken by Mexican forces in 1836" , "Famous Texan mission" .)