Anastrophe or the normal grammar?

As others have said in the comments, this sentence has the standard word order, so it is not anastrophic.

The subject is indeed a lot, but there is an ellipsis of the of-part that normally follows. Here is the relevant discussion from CGEL (p. 349, the emphasis in boldface mine). Most relevant to you are the B examples in [56]:

(a) Number-transparent quantificational nouns

The lot in

[53]  i a. [A lot of work] was done.        b.  [A lot of errors] were made.

is to be distinguished from that of We have two lots of visitors coming this afternoon, one at 2.30 and the other at 4, where lot is a count noun meaning "group". In the use illustrated in [53i] it has been bleached of its original meaning and is a non-count noun, with the bracketed NPs meaning respectively "much work" and "many errors". The of complement can be omitted in ellipsis, but it remains understood and continues to determine the number of the NP headed by lot, as is evident from the verb-forms in:

[56]  i  A: Where did all the money go?               B: A lot was spent on travel.
         ii  A: What happened to the protesters?     B: A lot were arrested.

In [i] a lot is understood as "a lot of the money" and hence is singular, in [ii] as "a lot of the protesters", and hence plural.

For completeness, let me include a more general discussion from this answer of mine. In both [531a] and [53ib], the subject (in brackets) is a noun phrase (NP) whose head is lot. But the number of the NP (i.e. whether the NP is singular or plural) is determined not by the head, as is normally the case, but by the number of the oblique (i.e. by the number of the complement of the preposition of): a lot of work is singular because work is singular, and so we have the singular verb was. And a lot of errors is plural because errors is plural, and so we have the plural verb were. We say that lot is a number-transparent quantificational noun. Besides lot and rest, there are only several other clear examples of number-transparent nouns: lots, plenty, bags, heaps, loads, oodles, remainder, number, and couple (CGEL, p. 350). In the words of CGEL, a number-transparent noun allows the number of the oblique to percolate up to determine the number of the whole NP (CGEL, p. 349).