Definitions of clinker:

• noun:   a hard brick used as a paving stone
• noun:   a fragment of incombustible matter left after a wood or coal or charcoal fire
• verb:   turn to clinker or form clinker under excessive heat in burning
• verb:   clear out the cinders and clinker from

  Example: "We clinkered the fire frequently"

• name:  A surname (very rare: popularity rank in the U.S.: #86654)