Obtains new defence (7)
I believe the answer is:
bastion
'defence' is the definition.
(bastion is a kind of defence)
'obtains new' is the wordplay.
'new' is an anagram indicator.
'obtains' is an anagram of 'BASTION'.
(Other definitions for bastion that I've seen before include "staunch supporter" , "Projecting part of a fortification" , "Fortified place near hostile territory" , "A projecting fortification to increase angle of fire" , "Obtains (anag.)" .)