Luxurious work, composing tune that has largo opening (7)
I believe the answer is:
opulent
'luxurious' is the definition.
(I know that luxurious can be written as opulent)
'work composing tune that has largo opening' is the wordplay.
'work' becomes 'op' (short for opus).
'composing' is an anagram indicator.
'that has' means one lot of letters goes inside another.
'opening' suggests taking the first letters.
The initial letter of 'largo' is 'l'.
'tune' is an anagram of 'uent'.
'uent' placed around 'l' is 'ulent'.
'op'+'ulent'='OPULENT'
(Other definitions for opulent that I've seen before include "Ritzy" , "Well-to-do, rich" , "Well-to-do or lavish" , "'Deluxe, luxurious (7)'" , "Well-to-dp. affluent" .)