Conductor first to condemn Placido's opening in short opera (6)
I believe the answer is:
copper
'conductor' is the definition.
(copper is a kind of conductor)
'first to condemn placido's opening in short opera' is the wordplay.
'first to' indicates taking the first letters.
'opening' indicates taking the first letters.
'in' means one lot of letters goes inside another.
'short' means to remove the last letter.
The initial letter of 'condemn' is 'c'.
The first letter of 'placido' is 'p'.
'opera' with its final letter taken away is 'oper'.
'p' going inside 'oper' is 'opper'.
'c'+'opper'='COPPER'
(Other definitions for copper that I've seen before include "Ductile metal" , "peeler" , "Reddish metallic element" , "Old policeman or reddish metal" , "Police officer (slang)" .)