1. a secure position, a firm basis for further progress
gain/get a foothold in sth
A 'foothold' is literally a place where someone can lodge their foot to support them when rock climbing. To get or gain a foothold means to have an established place or strong position from which to progress at a later time. You might hear someone talk about a company having 'a foothold in the market', for example. This phrase is used more often in professional contexts.