An Expect Further Clearance time is issued when ATC is not yet ready to give you an approach clearance but will issue some further instruction by that time. The further clearance might be a descent to a new altitude, a vector out of the hold, a frequency change, or even a revised EFC time.

"EXPECT FURTHER CLEARANCE AT (time)."

An EFC time is more general than an EAC time. It simply means ATC will not leave you in the hold indefinitely without contacting you.