Is it possible to control an led (+5V output) using a pin that is set to analog?
Yes, it's possible. But the technique required depends on how you are using the other Pins on PORTA.

Pins in analog mode can be put into output mode, and they will work just fine as long as no other Pins on that port are used for Digital input.

If another pin is using Digital OUTPUT, then a holding register can be used to eliminate the Read part of Read-Modify-Write.

If RA4 is an input to T0CKI, then that isn't considered a Digital input as far as R-M-W goes.

And yes, you can re-configure the analog ports "on-the fly", but that won't take care of the R-M-W problem if any of the pins are Digital INPUT.

What are the other pins on PORTA used for, and what is your current ADCON1 setting?
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