Eager or wary? Source of joy is absent, sleep instead (7)
I believe the answer is:
zealous
'eager' is the definition.
(synonyms)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for zealous that I've seen before include "Impassioned" , "Avidly enthusiastic" , "Showing great energy and enthusiasm" , "Highly enthusiastic" , "Very devoted to a cause" .)