Fortification (7)
There are a few possibilities for this:
battlement
'fortification' is the definition.
(I know that bastion is a type of fortification)
This is all the clue.
(Other definitions for bastion that I've seen before include "'Stronghold, citadel (7)'" , "Projecting part of a fortification" , "staunch supporter" , "Fortified place near hostile territory" , "Obtains in fortified place or stronghold" .)
'fortification' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for redoubt that I've seen before include "Keep losing confidence in" , "fortress" , "Obtrude in kind of military fieldwork" , "temporary defence work" , "Military defence-work" .)
'fortification' is the definition.
(bulwark is a kind of fortification)
This is the entire clue.
(Other definitions for bulwark that I've seen before include "defence" , "Defensive wall" , "Buttress" , "Fortification - side of ship above deck" , "Rampart" .)
'fortification' is the definition.
(battlement is a kind of fortification)
This is all the clue.
(Other definitions for battlement that I've seen before include "Top of a fortified wall" , "Crenellation" , "parapet" , "fortification" .)