Listening device open, hear poorly (8)
I believe the answer is:
earphone
'listening device' is the definition.
(I've seen this before)
'open hear poorly' is the wordplay.
'poorly' indicates an anagram.
'open'+'hear'='openhear'
'openhear' with letters rearranged gives 'EARPHONE'.
(Other definitions for earphone that I've seen before include "One can" , "Part of a headset" , "Hearing device" , "Personal sound receiver" , "Through which to hear privately" .)