The theme is revealed at 57A: One who lost what's hidden in 19-, 34- and 42-Across (Little Bo Peep), and what she's lost are found at:
19A: Bandleader in the Polka Music Hall of Fame (LAWRENCE WELK)
34A: Creamy soup (CLAM BISQUE)
42A: Substantial portion (FAIR AMOUNT)
The theme answers...and the whole puzzle, in fact...seemed awfully easy, even for a Monday. Maybe I was just on Lynn Lempel's wavelength. I'm curious to see what you thought.
A couple of really good long answers.
3D: Made a stand and would go no further (drew the line). Good phrase and well clued.
25D: "Fantastic Voyage" actress (Raquel Welch).
And some out-of-the-ordinary answers as well.
14A: Like a manly man (macho). Much better answer than the often-seen hairy. I know plenty of manly men who aren't.
38A: City where Van Gogh painted sunflowers (Arles)...if it's been in the puzzle lately, I don't remember it.
41A: Pacific republic (Nauru). Didn't know it but got it from crosses.
68A: Branch of Islam (Shia).
70D: Jean who wrote "Wide Sargasso Sea" (Rhys).
6D: Color of fall leaves (ocher). Ours are orange and red, although the wind yesterday and today blew most of them off. It was lovely while it lasted.
8D: Rhinoplasty (nose job).
43D: Latin American with mixed ancestry (Mestizo).
I struggled briefly in the southeast. Didn't know 55D: Explorer who proved that Greenland is an island (Peary). Didn't help that I couldn't remember the middle initial for 54A: New Deal program inits. (WPA). Don to the rescue...he knew WPA.
Of course I loved seeing 28A: Dance with a wiggle (hula) and 60A: Hawaiian isle (Maui) in the puzzle. Here we are on the beach in Maui...I think this is behind Mama's Fish House, the best place to eat on the island.
Time to wrap this up. Here's the grid...
...and I'll see you tomorrow.