Claim mischievous child has marvellous revolutionary jargon (9)

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

Claim mischievous child has marvellous revolutionary jargon BAG (=claim (for oneself), appropriate) + ELF (=mischievous child) + FAB (=marvellous); “revolutionary” indicates reversal; bafflegab is professional logorrhoea, often intended to confuse or obfuscate