I seem to have lost myself on the middle bottom square..
45 Across I ring following hard beating ? H ???n? .. My solution must be wrong .
53 Across Research leader is always after a subatomic particle (7) p?o???r
56 Across Bandage cloth impregnated with key Americam medicine (7) .. I am sure what I put in must be wrong ..
Finally 46 down A successful author knows to follow rising hero (7)
many thanks .. Rest of the damn thing seemed ok although I don't really understand how 11 down GROUNDHOG works ..