Some phantom alarmed back in place of historic siege (5)
I believe the answer is:
alamo
'place of historic siege' is the definition.
'Alamo' can be an answer for 'siege' (famous mission and siege from the Texas revolution). I'm unsure of the 'place of historic' bit.
'some phantom alarmed back' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'back' says the letters should be written backwards.
'omala' can be found hidden inside 'phantom alarmed'.
'omala' reversed gives 'ALAMO'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for alamo that I've seen before include "Historic Texas mission station" , "don't forget it!" , "Famous Texan fortress" , "The red planet" , "Fort in San Antonio, once famously besieged" .)