Love, dropping its first subtle shimmering (6)
I believe the answer is:
obtuse
'shimmering' is the definition.
Both the definition and answer are adjectives. Maybe you can see an association between them that I don't see?
I can't explain the rest of the clue.
(Other definitions for obtuse that I've seen before include "Slow of understanding" , "'Dense, slow (6)'" , "Angle greater than 90 degrees" , "Blunt or unintelligent" , "Exaggerate" .)