This is what I call a classic Sunday puzzle theme. It's right out of GAMES magazine from the old days. One word is put inside another to make a new word or phrase. What elevates this particular theme is the cleverness of the cluing: it's almost cryptic crossword style, with the exception that there is no reference to the finished product. Still, in each example, there's some term to indicate that one word is inside the other.
My favorite example is 68A: Flourishes around monsoon events (BRAINSURGEONS), or "rains" inside of "burgeons." Very nicely done. I also very much liked 28A: Neighborhoods surrounded by crime (THEFAREAST), or "areas" inside of "theft."
While all of the theme answers are clued well, I didn't think DRIVETRAINS stands up that well as its own phrase. Also, 116A: Crew found inside again and again (THROWINGRICE) doesn't work that well with the manipulated words. Why is "rowing" equal to "crew?" Shouldn't it be "rowers?"
Meanwhile, the rest of the grid is strong, as is to be expected from Mr. Chen, who pays very close attention to the quality of the fill. I feel sure he will remark on the "cheater" squares in the NW and SE corners, which likely improved those areas. Look at 18A and 18D, GRAVLAX and GROK. Beautiful combinations there. 1A: Per (APIECE) gets a C+, though, for its commonality.
Other nice entries include DOTTEDI, POSSECUT, and DULCINEA. 3D: Does his name ring a bell (IVANPAVLOV) and 124A: Need a lift? (SAG) are both GROANERS, but the former positively, the latter much less so.
I really have very little to complain about. Yes, there's AONE, NRA, and ECRUS (how can a color be pluralized?), but it was a fun Sunday.