Musical reduction shows top style (7)
I believe the answer is:
haircut
'top style' is the definition.
'haircut' can be an answer for 'style' (I have seen 'Tonsorial style ' mean 'haircut' so perhaps 'style' could also mean 'haircut'). I'm not certain of the 'top' bit.
'musical reduction' is the wordplay.
'musical' becomes 'hair' (1960s musical).
'reduction' becomes 'cut' (cut is a kind of reduction).
'hair'+'cut'='HAIRCUT'
'shows' is the link.
Can you help me to learn more?
(Other definitions for haircut that I've seen before include "Style of coiffure" , "Bob, say" , "that Damocles would have dreaded?" , "Mohican, possibly" , "Bob, perhaps" .)