promise somebody no less

Poor Mr. Butterbur looked troubled. 'You're right, master,' he said, 'and I beg your pardon. And I'm mortal afraid of what Gandalf will say, if harm comes of it. But I didn't keep it back a-purpose. I put it by safe. Then I couldn't find nobody willing to go to the Shire next day, nor the day after, and none of my own folk were to spare; and then one thing after another drove it out of my mind. I'm a busy man. I'll do what I can to set matters right, and if there's any help I can give, you've only to name it.

'Leaving the letter aside, I promised Gandalf no less. Barley, he says
to me, this friend of mine from the Shire, he may be coming out this way before long, him and another. He'll be calling himself Underhill. Mind that! But you need ask no questions. And if I'm not with him, he may be in trouble, and he may need help. Do whatever you can for him, and I'll be grateful, he says. And here you are, and trouble is not far off, seemingly.'

'What do you mean?' asked Frodo.

What does it mean in the first sentence of the second paragraph?