Stressful (4-8)
(Other definitions for high-pressure that I've seen before include "Stressful; persuasive" , "(Of selling) aggressively persistent" , "Aggressive, forceful" , "Aggressive (selling)" .)
(Other definitions for troubling that I've seen before include "causing distress" , "Burdensome" .)
'stressful' is the definition.
(I know that stressful can be written as trying)
This is all the clue.
(Other definitions for trying that I've seen before include "Taxing" , "Hearing (a case)" , "Causing strain, annoying" , "activity in court?" , "Tiresome" .)