Obscure bag filled with bananas is wishful thinking (5-6-4)

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

CLOUD (as a verb = obscure = to make something less visible) + LAND (as a verb = bag = to catch or otherwise achieve), containing CUCKOO (bananas = slang for crazy). Term derived from The Birds by Aristophanes, in which the birds build a new city in the sky: something that sounds like a nice idea but is unworkable or undesirable in practice.