As found in vaccines radiographer brought back (7)
I believe the answer is:
arsenic
'as' is the definition.
('arsenic' can be a synonym of 'as')
'in vaccines radiographer brought back' is the wordplay.
'in' indicates a hidden word.
'brought back' shows that the letters should be reversed in order.
'cinesra' can be found hidden inside 'vaccines radiographer'.
'cinesra' backwards is 'ARSENIC'.
'found' is the link.
(Other definitions for arsenic that I've seen before include "Ratsbane" , "Poisons in scare" , "Powerful poison" , "Poison used in pesticides and weedkillers" , "Toxic metallic element used as rat poison" .)