Singing: don't mess with Mr. In-Between! I recognized that lyric, but when I went to look up the song, Google misdirected me to a very different "Mr. In-Between" which seemed like it was the one the clue was talking about. Jim Horne had to steer me to the correct one. Then I realized that I had originally been thinking of a third song in the first place. So confusing!
Anyhoo, that MRINBETWEEN is such a kooky looking string of letters, and it makes for a good Monday revealer — phrases have MR stretched across them: BOTTOM ROW, STEAMROLLER, PALM READING, AM FM RADIO. All colorful phrases, and the one perhaps least in the language--BOTTOM ROW--getting a crossword-related clue. Nice!
Constructors often are faced with the choice of 1.) very smooth short fill but not so snazzy long stuff or 2.) really snappy long fill at the price of some short gluey bits. Today, Betty gives us a raft of wonderful bonus material, doing especially well with her mid-length answers: KABOOM!, FLUMMOX, IN ORBIT, NO, WAIT!, TWEEZE, EGG DYE. I'm usually not one to notice mid-length single-word answers, but KABOOM and FLUMMOX are especially nice.
Along with some longer fill like TORE OPEN and TITLEIST (sorry, non-golfers, but it really is a huge name in the golfing world), and a high density of theme answers, we were bound to get some compromises in the short fill. Starting off with A BANG isn't the type of bang I like, and along with LE ROI and IT IN right across the top, that's three glaring partials.
More troublesome were the ARNESS/LANTZ, LANTZ/GIZMO, ARNESS/ELS crossings. Regular solvers really ought to know James ARNESS and Ernie ELS (the "Big Easy" of golf). But I wouldn't be surprised to see a beginner get FLUMMOXed on any of those three crossings and declare them unfair. I wouldn't disagree.
Overall, nice theme concept with an enjoyable revealer, plus a ton of great mid-length fill. But given the rocky areas, I think it would have been better run as a Tuesday or Wednesday puzzle.