Robots do drains badly (8)
I believe the answer is:
androids
'robots' is the definition.
(android is a kind of robot)
'do drains badly' is the wordplay.
'badly' indicates an anagram.
'do'+'drains'='dodrains'
'dodrains' is an anagram of 'ANDROIDS'.
(Other definitions for androids that I've seen before include "Robots that resemble humans" , "Human-looking robots" , "Communication devices" , "Robots in human form as in science fiction" , "Automatons that resemble humans" .)