Observed screen did go haywire (9)
I believe the answer is:
discerned
'observed' is the definition.
(discern can mean to observe or notice)
'screen did go haywire' is the wordplay.
'go haywire' is an anagram indicator.
'screen'+'did'='screendid'
'screendid' is an anagram of 'DISCERNED'.
(Other definitions for discerned that I've seen before include "Distinguished, made out" , "Caught sight of" , "Identified by close investigation" .)