Musical boxes Tchaikovsky initially overlooked (5)
I believe the answer is:
chess
'musical' is the definition.
(Benny Andersson and Bjrn Ulvaeus musical)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for chess that I've seen before include "Sixteen-men-a-side game" , "In which two bishops will participate" , "form of battle" , "Ancient war game whose name may have derived for the Persian for 'king'" , "A game of skill" .)