Sleep like one and look good! (3)
I believe the answer is:
log
'sleep like one' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
'look good' is the wordplay.
'look' becomes 'lo' (archaic exclamation meaning 'look!').
'good' becomes 'g' (abbreviation).
'lo'+'g'='LOG'
'and' is the link.
Can you help me to learn more?
(Other definitions for log that I've seen before include "number in maths class?" , "Register" , "Official record; cut part of tree trunk" , "Chunk of wood" , "Ship's record" .)