No, not for a tattoo!

I have a Facebook group for beginning Irish students who want to read and translate simple Irish books. One of the books, Smuf, but Alan Titley is proving to be trickier than expected. For instance, one of our group members had a section that included the sentence Fear a raibh caipín air agus fuip ina lámh a d’oscail an doras. She did a nice job of translating it, but I have aquestion about the second a. It seems to me that the main clause is Fear . . . a d’oscail an doras.
What is the reason for that í? Is it because the fear has been fronted?

And then we have the expression for "next door" The dictionary (http://www.teanglann.ie/en/eid/next-door) has only b(h)éal dorais . Is there any rule that would explain why béal is not genitive?

Go raibh maith agaibh!

--Kathy

Yes, the main clause is Fear a d'oscail an doras.
Fear is fronted.

A man who had a cap (on him) and a whip in his hand opened the door.

béal dorais :
Béal dorais is a unity, a phrase; dorais is already in genitive ("mouth of door"), so béal doesn't change for genitive to avoid a double genitive. That's called "functional genitive".

Everywhere you could put brackets this way, double genitives don't occur:
[comharsa [béal dorais]] = [[Next door] neighbour]

Compare with:
[[Mála scoile] buachalla] = A [boy's [school bag]]
Double genitive because there's a "]" between both genitive nouns.

Thank you. That's very clear.