Small arrangement of minuet and air (9)
I believe the answer is:
miniature
'small' is the definition.
(similar in meaning)
'arrangement of minuet and air' is the wordplay.
'arrangement of' is an anagram indicator.
'and' is a charade indicator (letters next to each other).
'minuet' put after 'air' is 'airminuet'.
'airminuet' with letters rearranged gives 'MINIATURE'.
(Other definitions for miniature that I've seen before include "Tiny replica" , "Small-scale version" , "Smaller than normal" , "I ruminate (anag)" , "Diminutive" .)