Gloomy member, strikebreaker (8)
I believe the answer is:
blackleg
'strikebreaker' is the definition.
(I know that strikebreaker can be written as blackleg)
'gloomy member' is the wordplay.
'gloomy' becomes 'black' (I've seen this before).
'member' becomes 'leg' (member can mean a limb).
'black'+'leg'='BLACKLEG'
(Other definitions for blackleg that I've seen before include "one not out, controversially" , "Person who works while others are on strike, having dark limb" , "Scab, strikebreaker" , "Strikebreaker - disease of farm animals" , "One who breaks a strike by working" .)