It's not. It's just the "T" sound from the previous word running on to the "YA" sound in "jakkesæt".
Can you also say: 'the mother has a green jacket,' or is that something completely different?
"The mother has a green jacket" is "Møren har en grøn jakke." Luckily, Danish is related to English, and jakke's form is closer to jacket, while jakkesæt's form is a bit closer to suit.