Old store drapes upper class clothing line lavishly (9)
I believe the answer is:
opulently
'lavishly' is the definition.
(thesaurus)
'old store drapes upper class clothing' is the wordplay.
'old store drapes' becomes 'opulent' (I am not sure about this - if you are sure you should believe this answer much more).
'upper class' becomes 'landed gentry' (landed gentry is a kind of upper class).
'clothing' means to remove the middle letters.
'landedgentry' with its centre taken out is 'ly'.
'opulent'+'ly'='OPULENTLY'
'line' acts as a link.
I am not very happy about this link. It may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for opulently that I've seen before include "in lavish manner" , "With wealth on view" , "like millionaires" .)