@@ -23 +23 @@
-<gloss>main street (as opposed to a back street)</gloss>
+<gloss>main street (as opposed to a side street)</gloss>

GG5: 〔本通り〕 a 「main [high] street; a main thoroughfare.
中辞典: 〈家の前の通り〉 the street in front of one's house; 〈大通り〉 《米》 a main street; 《英》 a high street.
Daijr: 町の主要な道路。

I think this is clearer.
裏通り is not really an antonym, I think Daijisen was just contrasting.

@@ -22,3 +22,3 @@
-<xref type="ant" seq="1550490">裏通り</xref>
-<gloss>the street (as opposed to back streets)</gloss>
-<gloss>the streets</gloss>
+<xref type="see" seq="1550490">裏通り</xref>
+<gloss>main street (as opposed to a back street)</gloss>
+<gloss>high street</gloss>

Daijisen posits “裏通り” as an antonym: https://kotobank.jp/word/表通り-454880
Google's dictionary describes it in general terms: https://www.google.com/search?q=表通り+とは
In the Tsukuba web corpus, I could not find a usage that uses the word as “Main Street”: https://tsukubawebcorpus.jp/headword/N.20018/en/

“Main street” may cause confusion: I've experienced people interpreting that as “Main Street” – i.e. the singular most “important” street of a town, which is how all the English dictionaries I referenced defines the term. The word, however, just refers to *a* sizable non-alleyway street. I suspect the initial entry of “main street” might have come from how it's unclear whether dictionaries' typical short descriptions (e.g. “市街の主要な道路”) leave it ambiguous whether it's indefinite (“a 主要な道路”) or definite (“the 主要な道路”).

The term “the street” here is in the sense used in, say, the sentence “He was busking in the street.”, whereas “the streets” is as in “Nothing says ‘opulent’ like the streets of Ginza.”

@@ -22 +22,3 @@
-<gloss>main street</gloss>
+<xref type="ant" seq="1550490">裏通り</xref>
+<gloss>the street (as opposed to back streets)</gloss>
+<gloss>the streets</gloss>

@@ -9,0 +9,4 @@
+</k_ele>
+<k_ele>
+<keb>表通</keb>
+<ke_inf>&io;</ke_inf>