ACFT IN POS AND HOLD RECEIVES AMENDED CLRNC AND BELIEVES A TKOF CLRNC.

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WE WERE DEPARTING LAX TO THE E. AFTER RECEIVING A CLRNC TO 'TAXI INTO POS AND HOLD 7L' BOTH THE FO AND I HEARD THE FOLLOWING CLRNC: 'FLT ABC; AFTER DEP FLY RWY HDG; MAINTAIN AT OR BELOW 2000 FT UNTIL LAX 7 DME; MAINTAIN 5000 FT; CLRED FOR TKOF.' I READ BACK THE CLRNC AND ASKED THE CTLR; 'IS THAT CORRECT?' AND RECEIVED AN AFFIRMATIVE REPLY. IT IS IMPORTANT TO NOTE THAT BOTH THE FO AND I INDEPENDENTLY HAD ACCOMPLISHED THE STANDARD PROCS REGARDING ACFT LIGHTING AND MECHANICAL CHKLIST ITEMS THAT ARE ONLY DONE AFTER A CLRNC FOR TKOF HAS BEEN RECEIVED. AT APPROX V1; THE TWR BEGAN A XMISSION: 'FLT ABC; WIND 170 AT 11 CLRED FOR ...' AND TRAILED OFF. SHE THEN INFORMED US WE HAD NOT RECEIVED A TKOF CLRNC; BUT TO CONTINUE AND 'DON'T WORRY ABOUT IT.' WE CONTINUED OUR DEP WITHOUT FURTHER ADO. NO LOSS OF SEPARATION HAD OCCURRED. FACTORS CONTRIBUTING TO THIS SIT WERE THE NUMBER OF ACFT THAT THE CTLR WAS WORKING; INCLUDING A FOREIGN CARRIER THAT WAS CAUSING SOME CONFUSION. ALSO; THE CLRNC WE RECEIVED WAS A CHANGE FROM OUR ORIGINAL CLRNC. TO PREVENT A RECURRENCE OF THIS I FEEL THAT AMENDED TKOF INSTRUCTIONS THAT DO NOT INCLUDE A CLRNC TO TKOF SHOULD BEGIN WITH: 'CONTINUE HOLDING; AFTER DEP EXPECT ....' IF WE DID NOT RECEIVE A CLRNC FOR TKOF; THEN WHAT WE GOT WAS POORLY PHRASED AND ILL TIMED.