。
It's absolutely not a leisurely job.
Literal
Absolutely leisurely [attributive-な] work is-not-[ではない].
決して ('absolutely, by no means') is a strong negative intensifier that pairs with a negative predicate. 悠長 ('leisurely, relaxed, unhurried') often carries a faintly critical tone — implying things should be done more urgently. The sentence denies that the work is leisurely, implying it's actually urgent or demanding.