Whistle-blower inconclusive on promise not to reveal votes (9)

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

REFERE e (whistle blower) missing last letter or ‘inconclusive’ NDA (non disclosure agreement – ‘promise not to reveal’). We only parsed this one when we were writing up the blog as we both had REF for whistle blower.