Threatened over suppressing fury (10)
I believe the answer is:
endangered
'threatened' is the definition.
('endanger' can be a synonym of 'threaten')
'over suppressing fury' is the wordplay.
'over' becomes 'ended' (over can mean finished or ended).
'suppressing' means one lot of letters goes inside another.
'fury' becomes 'anger' (fury is intense anger).
'ended' enclosing 'anger' is 'ENDANGERED'.
(Other definitions for endangered that I've seen before include "compromised" , "put at risk" , "Vulnerable" , "in a perilous situation" , "Like some species" .)