Defensive position of British PM falling short, intended to be heard (10)
I believe the answer is:
battlement
'defensive position' is the definition.
(I know that battlement is a type of defensive position)
'british pm falling short intended to be heard' is the wordplay.
'british pm falling short' becomes 'battle' (I can't justify this - if you can you should believe this answer much more).
'intended' becomes 'meant' (to mean something is to intend it).
'to be heard' shows a homophone (sound like).
'meant' sounds like 'ment'.
'battle'+'ment'='BATTLEMENT'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for battlement that I've seen before include "Crenellation" , "fortification" , "parapet" , "Top of a fortified wall" .)