Chief items contained in line assets (10)
I believe the answer is:
essentials
'chief items' is the definition.
Although both the answer and definition are plural nouns, I can't see how they can define each other.
'contained in line assets' is the wordplay.
'line assets' can be anagrammed to 'ESSENTIALS'.
Though, I am not clear how the anagram is indicated.
Can you help me to learn more?
(Other definitions for essentials that I've seen before include "Things needed" , "necessities" .)