Unfortunately there is no one foundation that can help disguise a shadow. The best thing to do is try to compensate and correct it with a light reflecting powder or foundation that will help to bounce light away from the area, thus illuminating it.
Guerlain Precious Light Smoothing Illuminator, £23 (01932 233 909) will help do the trick. This paint-on concealer-come foundation has a precise paint-brush type tip so it's easy to apply without over-loading your skin (too much product will cling to the hair and only serve to over-emphasise the problem).