AN MD88 FLT CREW TAXIED ONTO RWY 23L AT RDU WITHOUT CLRNC.

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DURING TAXI OUT TO RWY 23L ON TXWY A; TWR INSTRUCTED US TO MOVE TO THE INNER TXWY J AT J2. THIS WAS BECAUSE WE HAD BEEN ASSIGNED A 10 MIN HOLD TO DEPART AND TWR WANTED TO ALLOW OTHER ACFT TO DEPART. I POSITIONED THE ACFT ONTO TXWY J HOLDING SHORT OF J3. I INSTRUCTED THE COPLT TO LEAVE BOTH ENGS RUNNING; BUT TO CONFIGURE THE BLEED SYS TO ALLOW THE APU TO RUN THE AIR CONDITIONING PACKS FOR MORE EFFECTIVE COOLING. SEVERAL ACFT DEPARTED FROM RWY 23L AND A REGIONAL JET WAS TOLD TO HOLD SHORT TXWY A8 ON TXWY A. TWR THEN ISSUED THE INSTRUCTION; 'TAXI AROUND AND IN FRONT OF THE RJ.' I DO NOT RECALL A 'HOLD SHORT' INSTRUCTION; NOR DO I RECALL A 'POS AND HOLD' INSTRUCTION. THE COPLT RESPONDED AND THEN I BEGAN TO TAXI TO THE NE EDGE OF TXWY A8 IN ORDER TO INSURE WINGTIP CLRNC WITH THE NOSE OF THE RJ. AFTER ACFT MOVEMENT; I TOLD THE COPLT TO RECONFIGURE THE BLEEDS FOR TKOF AND RUN THE BEFORE TKOF CHKLIST AGAIN TO INSURE PROPER BLEED CONFIGN FOR TKOF. HE WAS RUNNING THE CHKLIST AS I WAS TAXIING THE ACFT TOWARDS THE RWY. I PERCEIVED THE TWR INSTRUCTION 'TAXI AROUND AND IN FRONT OF THE RJ' TO MEAN CLRNC ONTO THE RWY. WE TAXIED APPROX 20 FT PAST THE HOLD LINE WHEN THE COPLT FINISHED THE CHKLIST AND QUERIED ME IF WE WERE CLRED ONTO THE RWY. I STOPPED THE ACFT AND WE CALLED TWR TO INQUIRE ABOUT OUR CLRNC. TWR THEN SAID TO HOLD SHORT OF THE RWY. THERE WAS A TWIN ENG PROP ON APPROX A 4 MI FINAL TO RWY 23L THAT WAS SENT AROUND. THE PROB AROSE WITH MY MISINTERP OF THE TWR INSTRUCTION; 'TAXI AROUND AND IN FRONT OF THE RJ.' TASKING THE COPLT WITH A CHKLIST DURING THIS TOOK HIM OUT OF THE LOOP UNTIL IT WAS TOO LATE. MY CONCERN WITH WINGTIP CLRNC ON THE RJ SHIFTED MY FOCUS OFF OF A NONSTANDARD CLRNC WHICH I SHOULD HAVE CLARIFIED. I WAS ALSO ON MY THIRD CONSECUTIVE DUTY DAY COMING UP ON 7 HRS ON DUTY.