Dictator, in reality, ran tests (6)
I believe the answer is:
tyrant
'dictator' is the definition.
(I have seen 'Cruel dictator ' mean 'tyrant' so perhaps 'dictator' could also mean 'tyrant')
'in reality ran tests' is the wordplay.
'in' indicates a hidden word.
'TYRANT' can be found hidden inside 'reality ran tests'.
(Other definitions for tyrant that I've seen before include "Harsh and absolute ruler" , "taskmaster" , "Autocrat or despot" , "Despotic ruler" , "Arbitrary ruler" .)