、。
It might be a trap — don't let your guard down.
Literal
Trap might-be, carelessness do-not.
かもしれん is the masculine/brusque contraction of かもしれない. 油断するな uses the prohibitive imperative (するな = 'don't do'). The terse, imperative tone marks this as an urgent warning — probably a military, gaming, or action-drama context. Two short clauses without connective particles, building tension.