Frightening hanger from wood classed 'poor' (5,2,8)
I believe the answer is:
sword of damocles
'frightening hanger' is the definition.
(something which hangs forebodingly)
'from wood classed poor' is the wordplay.
'poor' indicates anagramming the letters.
'from'+'wood'+'classed'='fromwoodclassed'
'fromwoodclassed' is an anagram of 'SWORD OF DAMOCLES'.
(Other definitions for sword of damocles that I've seen before include "It was perilously poised overhead" , "precarious situation" , "Imminently impending peril, disaster" , "imminent threat" , "Impending threat" .)