Break The Deadlock Meaning

(idiomatic, sports) To score the first goal or point in a competition

Example: 2011 January 8, Chris Bevan, “Arsenal 1 - 1 Leeds”[1], BBC:
  The Gunners continued to press after the break but it was Leeds who broke the deadlock in the 54th minute. There was no doubt about the penalty either, with Denilson clumsily fouling Gradel and Snodgrass stepping up to find the bottom corner of the net.