Definitions of foothold:

• noun:   a place providing support for the foot in standing or climbing
• noun:   an initial accomplishment that opens the way for further developments

  Example: "They are presently attempting to gain a foothold in the Russian market"

• noun:   an area in hostile territory that has been captured and is held awaiting further troops and supplies

  Example: "The only foothold left for British troops in Europe was Gibraltar"