Even mild sleep is good for nothing (4)
I believe the answer is:
idle
'good for nothing' is the definition.
Both the definition and answer are adjectives.
Perhaps there's a link between them I don't understand?
'even mild sleep' is the wordplay.
'even' means one should take alternating letters (even-numbered letters are used).
'mild'+'sleep'='mildsleep'
The alternate letters of 'mildsleep' are 'IDLE'.
'is' is the link.
Can you help me to learn more?
(Other definitions for idle that I've seen before include "Lied about doing nothing" , "Lazy - vain" , "Not doing much" , "without purpose" , "without basis" .)