San Antonio landmark (5)
'san antonio landmark' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for alamo that I've seen before include "Mission building in Texas, site of famous siege by Mexico" , "Where Jim Bowie died" , "Davy Crockett's last stand" , "Texas mission taken by Mexican forces in 1836" , "don't forget it!" .)
(Another definition for the alamo that I've seen is " battle site".)