How to Complete It's a Trap!
The objective is to destroy all of the traps. The traps are all marked, so you just need to walk onto them to destroy them. Unfortunately, your units will be injured/debuffed whenever they step on these traps, although they can avoid debuffs if they are equipped with protection against those debuffs.
There are three Baknamys and a Luchorpan on the field, but you can ignore them if you wish. You only have to destroy the traps to complete the quest.