Taking the most pessimistic view, tort was shocking (2,5)
I believe the answer is:
at worst
'taking the most pessimistic view' is the definition.
(said before identifying the worst case scenario)
'tort was shocking' is the wordplay.
'shocking' indicates anagramming the letters (letters shocked or shaken).
'tort'+'was'='tortwas'
'tortwas' with letters rearranged gives 'AT WORST'.
(Other definitions for at worst that I've seen before include "most pessimistically" , "in the most serious state" , "Taking the most pessimistic view" , "In the most negative circumstances" , "Taking blackest view" .)