Group sleep lightly before noon (5)
I believe the answer is:
dozen
'group' is the definition.
Both the answer and definition are adjectives. Perhaps you can see an association between them that I don't see?
'sleep lightly before noon' is the wordplay.
'sleep lightly' becomes 'doze' (I've seen this before).
'before' says to put letters next to each other.
'noon' becomes 'n' (abbreviation).
'doze'+'n'='DOZEN'
Can you help me to learn more?
(Other definitions for dozen that I've seen before include "One less than 13" , "Twelve (or thirteen for a baker?)" , "Quantity of e.g. eggs" , "Twelfth of a gross" , "Group of 12" .)