Significant pair of musical works, back-to-back with common ending (9)
I believe the answer is:
operative
'significant' is the definition.
(I've seen this before)
'works back-to-back with common ending' is the wordplay.
'works' becomes 'opera' ('opera' is an alternative plural of 'opus').
'back' is a reversal indicator.
'to back with common ending' becomes 'evit' (I can't justify this - if you can you should give a lot more credence to this answer).
'evit' written backwards gives 'tive'.
'opera'+'tive'='OPERATIVE'
'pair of musical' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for operative that I've seen before include "Machinist - working" , "Worker in manufacturing" , "Efficient" , "Having force - skilled worker" , "desired effect" .)