What orchestra does initially to keep protest going (6,2)
I believe the answer is:
strike up
'what orchestra does initially to keep' is the definition.
The definition suggests a comparative adjective but the answer is not.
'protest going' is the wordplay.
'protest' becomes 'strike' (strike is a kind of protest).
'going' becomes 'up' (I can't explain this - if you can you should give a lot more credence to this answer).
'strike'+'up'='STRIKE-UP'
Can you help me to learn more?
(Other definitions for strike up that I've seen before include "Start playing music - begin (acquaintance) - emboss" , "Begin to play (a piece of music)" .)