Arranged diamonds in elaborate decoration (11)
I believe the answer is:
coordinated
'arranged' is the definition.
Both the definition and answer are adjectives. Maybe there's a link between them I don't understand?
'diamonds in elaborate decoration' is the wordplay.
'diamonds' becomes 'd' (abbreviation for the card suit diamonds).
'in' indicates putting letters inside.
'elaborate' indicates an anagram (an elaborate version of the letters).
'decoration' is an anagram of 'coorinated'.
'd' inserted within 'coorinated' is 'COORDINATED'.
Can you help me to learn more?
(Other definitions for coordinated that I've seen before include "Attractively harmonised" , "Matched, harmonised" .)