'An' or 'a' when followed by information between commas

In the following sentence, I'm unsure whether to use ‘an’ or ‘a’.

..primarily meant as a, albeit large, donation.

On the one hand ‘an’ sounds more appropriate when read, as the vowel beginning to ‘albeit’ suggests.
Alternatively, one might say ‘a’ is correct; is a sentence not supposed to make perfect sense with the word between the commas removed. If so, it must be just an ‘a’.

I'm tilting towards the latter, even though it sounds odd. Please enlighten me.

Answer

Are you stuck with this very awkward sentence construction? Since you are questioning what article to use, I suspect you are not. Therefore, I suggest that you change the sentence construction:

     ....primarily meant as a donation, albeit a large one.

That gets you around all of your problems.