There are five entries that don't really fit the clues. In some versions of the puzzle they are marked with asterisks but in the harder versions they are unmarked.
a MAYFLY20AInsect with forelimbs similar to a mantis[------] doesn't have mantis-like appendages' SEND21ATo signal[----] doesn't really mean to signal. There never really were FADs about those stinky foods. To outdo ... well it is to BEST53ATo out-do in an activity[----], but BEST53ATo out-do in an activity[----] doesn't indicate any particle activity that one is BESTing another in and "in an activity" was an essential part of the clue. And RETIRED59AFixed and ready for use again[-------]
doesn't mean "fixed and ready to use".
These clues have mistakes and you must "rise above it all" and look into the entry above to fix them. In some of the puzzles the clues of the entries above or are marked with a + but in the harder ones they are unmarked.
If you rise above the middle Y in MA(Y)FLY you have the (NTIS) in deNTISt and if you replace the Y with that you have the correct answer MA(NTIS)FLY. Likewise S(E)ND becomes S(OU)ND, F(A)D becomes F(ETI)D, BE(S)T becomes BE(ATA)T and RE(T)IRED becomes RE(PA)IRED which all fit the clues better.
So what was the "it all" you had to rise above? Y-E-A-S-T