Depends, if you just want to pass the mission it's easy. As soon as you get there, change your navpoint to the Tiger's Claw then turn around and afterburn till the autopilot light turns on then press A. Next go back to the Ralari, when you get there it's gone, and the Gratha's are on their own. Kill them then check your navmap, the Ralari is near the Tiger's Claw now, fly to it then fly with it to the Tiger's Claw.
Proper way involves volley's of missiles, telling Bossman to attack, ramming and much abuse over the com and a fair amount of luck. I'm sure someone else can explain it better in how to do it.