 What kind of literary device is being used in the story’s title?
The gold-braided hat of his trade was not clamped in its usual belligerent position slightly over one eye. He had foisted those two maudlin mastodons off onto me in one of our earlier deals, and if I had somehow been responsible for his present troubles, it was no more than he deserved. Transshipped seeds invariably failed to germinate, which explained its rarity. But when I offered them a sizable piece of cash plus a perpetual share of the profits for letting us take a load of marocca plants to Gloryanna III, they relented and, for the first time in history, gave their assent. Days and nights the same length and no seasons—that means no ecliptical and no axial tilt. If we had gone through all of that rigamarole, we would have lost the franchise. I almost asked him why he had been barricaded in the bathroom of the Delta Crucis , but I figured it was safer to let him tell me in his own way, in his own time. And by the time I had lined up for Gloryanna and Jumped, I figured, like you said, that the trip would be a cakewalk. In Limbo, moving at multiple light-speeds, the whole Universe, of course, turns into a bright glowing spot in our direction of motion, with everything else dark. So I lined up the Delta Crucis perpendicular to her direction of motion, put a once-every-twenty-one hour spin on her to match the rotation rates of Mypore II and Gloryanna III, and uncovered the view ports to let in the light. It gradually brightened until 'noon time', with the ports pointing straight at the light source, and then dimmed until we had ten and one-half hours of darkness. With no gravity for reference, how were the plants supposed to know that the 'sun' was supposed to be moving?" I just put enough spin on the ship to make artificial gravity, and then I strung a light and moved it every fifteen minutes for ten and one-half hours, until I had gone halfway around the room. "Of course, first I had to move all the hydroponic tanks from their original positions perpendicular to the axial thrust line of the ship to a radial position. And because somehow we had picked up half of the plants in the northern hemisphere of Mypore and the other half in the southern hemisphere, it turned out that half of the plants had a sinistral corkscrew and the other half had a dextral.
 Irony: Captain Hannah faces so many trials and tribulations during his time with the plants that his voyage is very much NOT a cakewalk to Gloryanna.
 Metonymy: “Cake Walk” is a literal attribute/adjunct for the part of the ship Captain Hannah grows the marocca in.  Irony: Captain Hannah faces so many trials and tribulations during his time with the plants that his voyage is very much NOT a cakewalk to Gloryanna.  Metaphor: Cake walk is a metaphor the narrator uses to describe Captain Hannah’s journey once complete. They were both surprised at the venture’s absurd ease.  Euphemism: “Cake walk” is used by the narrator to politely suggest that the plants had their way with Captain Hannah.