Supports the defensive efforts (6)
I believe the answer is:
stands
I believe this clue is a double definition.
'supports' is the first definition.
(stand is a kind of support)
'defensive efforts' is the second definition.
(I've seen this in another clue)
'the' is the link.
(Other definitions for stands that I've seen before include "Remains unchanged" , "Puts up with" , "doesn't change" , "Stadium seats" , "Remains upright" .)