SF340 ACFT HAD BEEN CLRED BY TWR TO CROSS RWY. RPTR FLC HEARD ANOTHER COMPANY THEN CLRED ON TO THE RWY THEY WERE SUPPOSED TO CROSS; BUT DIDN'T HEAR CLRLY THAT THE ACFT HAD BEEN CLRED INTO POS AND HOLD. RPTR WAS CONCERNED THAT THEY WOULD BE TAKING OFF IMMEDIATELY SO STOPPED TAXIING; BUT OVER THE HOLD SHORT LINE. FREQ CONGESTION INTERFERED WITH CLARIFICATION COM. BY THEN ANOTHER ACFT WAS LNDG ON ANOTHER RWY SO TWR CLRED THE POS AND HOLD ACFT TO TKOF THEN AFTER THE LNDG MD80 HAD LANDED TWR CLRED RPTR ACROSS.

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WHILE 'HOLDING SHORT' OF RWY 17C; DFW ARPT; ON TXWY 'Z' (W OF RWY 17C). TWR CLRED MY ACFT TO 'CROSS RWY 17C. TAXI TO RWY 13L.' JUST PRIOR TO THIS CLRNC; THE CTLR CLRED A COMPANY ACFT HOLDING SHORT OF RWY 17C AT 'YANKEE' (TXWY 'Y') W OF RWY 17C TO TAXI 'INTO POS AND HOLD RWY 17C' IN PREPARATION FOR TKOF. MY FO AND I DID NOT CLRLY HEAR THE POS AND HOLD CLRNC; AND AFTER TAXIING PAST THE HOLD SHORT LINES; I STOPPED TO AVOID A POSSIBLE CONFLICT WITH THE COMPANY ACFT IN POS FOR TKOF. REGIONAL AIRLINE TKOFS FROM RWY 17C ARE ALMOST ALWAYS 'CLRED FOR IMMEDIATE' TKOFS WHICH ALSO CAUSED ME TO STOP. FREQ CONGESTION DELAYED CLARIFYING SIT WITH TWR. DESPITE TELLING CTLR I WAS STOPPED 'PAST THE HOLD SHORT LINE;' HE AGAIN TOLD ME CROSS THEN TOLD ME TO STOP AND CLRED COMPANY TO TKOF RWY 17C. BECAUSE AN MD80 WAS ON SHORT FINAL AND CTLR WAS BUSY HE COULDN'T CLR ME TO CROSS RWY 17C PRIOR TO THE MD80 LNDG. THIS SIT WAS CLRLY UNSAFE AND COULD HAVE BEEN AVOIDED SEVERAL DIFFERENT WAYS. IF CTLR HAD CLRED MY ACFT FIRST TO CROSS RWY 17C I WOULDN'T HAVE BEEN CONCERNED ABOUT TAXIING IN FRONT OF ACFT IN POS AND HOLD FOR TKOF. IF MY FO AND I HAD HEARD OUR COMPANY CLRED INTO POS; I COULD HAVE CONTINUED HOLDING SHORT AND CLARIFIED THE CLRNC WITHOUT INTRUDING ONTO THE RWY.