AN ACR MLG WAS GIVEN AN AMBIGUOUS; IMPROPERLY WORDED DSCNT CLRNC THAT LED TO LTSS.

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ISSUED A CLRNC TO CROSS WISKE AT 10000 FT MSL. LATER ATC REQUESTED THAT WE 'START DOWN NOW TO 14000 FT.' WE INTERPRETED THIS TO MEAN WE WERE TO DSND TO 14000 FT NOW AND THEN CROSS WISKE AT 10000 FT. A TFC CONFLICT OCCURRED AT 13000 FT. TCASII ISSUED A TA CORRECTLY SINCE WE WERE PASSING BEHIND XING TFC. WE SAW THE TFC JUST PRIOR TO THE TCASII TA. THE CTLR CALLED THE TFC LATER. I TALKED WITH ZOB BY TELEPHONE AND THEY WERE QUICK TO SAY 'PLTDEV HAS OCCURRED.' LATER; AFTER THEY HAD LISTENED TO THE TAPES; THEY SAID; 'IT LOOKS LIKE IT WAS CTLR ERROR.' SUPPLEMENTAL INFO FROM ACN 339075: DSNDING THROUGH 12000 FT; THE CTR SAID WE WERE SUPPOSED TO STOP AT 14000 FT. IN THE PREVIOUS CTR CLRNC; MAINTAIN 14000 FT WAS NEVER GIVEN. THERE WAS NEVER ANY DOUBT BTWN MYSELF AND CAPT THAT THE 'WISKE' AT 10000 FT RESTR WAS OUR CLRNC LIMIT. SUPPLEMENTAL INFO FROM ACN 339076: I CLRED ACFT X TO 10000 FT. SHORTLY AFTERWARD; I REALIZED ACFT Y WOULD NOT BE CLR OF ACFT X RTE; SO I TRIED TO STOP ACFT X AT 14000 FT. PLT SAID OK; BUT NEVER STOPPED AT 14000 FT AND I LOST SEPARATION WITH ACFT Y AT 13000 FT.