Need millions to engage in encouragement to repeat main Waugh novel (13)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

Need millions to engage in encouragement to repeat main Waugh novel [LACK (=need, want) + M (=millions)] in [BIS (=encouragement to repeat, in music) + CHIEF (=main, principal)]; the reference is to the 1932 novel by Evelyn Waugh, set on the fictional African island of Azania