One, two, three, SIXWAYSTOSUNDAY! A fun theme, and a nice reminder of Frannie's mom, who used to use that expression. The three themers adding up to the revealer are solid, although some may argue that THREEWAYTIE is a tad ad hoc.
There are many quality bits of fill in this one: TOPSECRET (14A: Highly classified) is fun, and PINGPONG (45A: Table tennis) ought to please Mr. Fob as much as it must please Mr. Shortz himself, as I know both of those men enjoy the game. There's the nutty cross of PEANUTS and PECAN, with BEECH in symmetry at the bottom, and at the bottom, a TREESTUMP. I like GETBUSY (46D: "Hop to it!") and EATUP (26D: Readily accept) for their colloquialness.
Starting with SHO (1A: "Penny Dreadful" channel, for short) (D) is unfortunate, and there's EDUC, ASST, OED, SEL, and a few other bits of the usual glue, but overall, I thought this a good Monday, and especially good for a debut! I'll look forward to seeing Mr. Wrenholt's byline on a Tuesday next, as he works his way through the week.