have a grasp of

have a (good/solid/sound/etc.) grasp of/on (something)

To have a firm, clear understanding or determination of something. I hope everyone has a solid grasp of the material, as you'll be tested on it next week. I thought I had a pretty good grasp on English idioms, but I don't understand this one at all!See also: grasp, have, of, on, solid, sound

have a grasp of

see under get a fix on. See also: grasp, have, of