Two assumptions: Non-radar handling and "conventional" i.e. radios, not RNAV. Yes, I am aware of FAR 91.175 and NoPT routings and timed approaches over the FAF.
An ATC clearance cannot supersede the requirement to begin an approach at an IAF. ATC does not have the authority to do that.
The only exceptions involve radar and per your assumptions above, it is not available.