Nurse upset by journalist - that's guaranteed (7)
I believe the answer is:
ensured
'guaranteed' is the definition.
('ensure' can be a synonym of 'guarantee')
'nurse upset by journalist' is the wordplay.
'upset by' indicates anagramming the letters.
'journalist' becomes 'ed' (short for editor).
'nurse' with letters rearranged gives 'ensur'.
'ensur'+'ed'='ENSURED'
'that's' acts as a link.
(Other definitions for ensured that I've seen before include "Saw to it" , "Made certain, clinched" , "Make certain of" , "Made certain for end user" , "Determined" .)