I don't know how you are generating the clock (OSC2 perhaps?), but you can probably just put a 2.2K resistor (or so) from that pin to RB0 and then connect RB0 to the smart card.

The program code
TRISB.0 = 1 will allow the line to toggle
and the lines
PORTB.0 = 0
TRISB.0 = 0
will force it low.

All this assumes that your smart card can tolerate the 2.2K resistor in the clock line.