Translation:They are staying in the north for a year.
That was my understanding — that ar feadh translates “for” in the sense of “throughout” or “during”, so it’s better suited to describing completed events. Either le bliain or go ceann bliana would fit better here.
EDIT #1: The NEID offers the following examples under “year”:
we've been waiting for a year táimid ag fanacht le bliain
we'll be there for a year beimid bliain ann, beimid ann ar feadh bliana
I haven't seen her for a year ní fhaca mé í le bliain
These examples have different tenses than the examples in the FGB. The most interesting example of these to me is the one that uses bliain as a direct object, which suggests that Tá siad ag fanacht bliana thuaidh would be possible.
Also, it seems as though the future progressive would be necessary for this sentence — Beidh rather than Tá — since present tenses aren’t used for the future in Irish as they can be in English.
EDIT #2: Tá siad ag fanacht bliana thuaidh wouldn’t work, since it would only be used to describe the duration of a pause.
EDIT #3: This exercise would be OK as is if it were translated into the English present perfect — “They have been staying in the north for a year”.
EDIT #4: German Gramadach na Gaeilge notes that ar feadh doesn’t have to be used for the past if the duration of the event is in the foreground of the sentence.
The audio of this question does not match answer. The audio sounds like "thainig na feirmeoiri ag duig o Londain go Paras", see actual answer in other comments. I don't have fada abilities on this device. How am I meant to guess the answer that does not match audio, seriously how?