Hospital nurses register The War Cry (6)
I believe the answer is:
slogan
'the war cry' is the definition.
(thesaurus)
'hospital nurses register' is the wordplay.
'hospital' becomes 'san' (I've seen this in other clues).
'nurses' is an insertion indicator.
'register' becomes 'log' (I've seen this before).
'san' going around 'log' is 'SLOGAN'.
(Other definitions for slogan that I've seen before include "Memorable advertising phrase" , "advertising catch phrase" , "Battle cry - advertising phrase" , "Logo" , "Advertising catchphrase" .)