Avis rival (5)
I believe the answer is:
alamo
'avis rival' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for alamo that I've seen before include "Site of 1836 massacre in Texas" , "Texas mission taken by Mexican forces in 1836" , "national monument" , "Famous Texan fortress" , "The --, Texan mission besieged in 1836" .)