Emotion that is dangerous? Not entirely (5)
I believe the answer is:
anger
'emotion' is the definition.
(anger is an emotion)
'that is dangerous? not entirely' is the wordplay.
'not entirely' says the answer is hidden in the clue.
'ANGER' can be found hidden inside 'that dangerous'.
(Other definitions for anger that I've seen before include "Wrath, fury" , "Spleen" , "Hot displeasure; enrage" , "Irateness" , "Hack off" .)