Great improvement on last week, though some obscurities ('pleistocene', 'idola') meant more Googling than I like.
Stuck with these.
27a Crustacean current lawmaker found crossing Italian river? (6)
Isopod? I = current, Italian river = Po, but how does sod = lawmaker?
3d Dread losing son before sharp double bend: you must cross that river! (7)
Looks like ‘Yangtze’, can't begin to parse it though.
46d Sound iron chest primarily containing lead (7)
P?u?b?c