There's no single Qabil that can defeat Al Shabab, none. They might get defeated for a few years or months but they will eventually be back as is the case everywhere in Somalia.
If XL defeat Alshabab they will just leave and go to another place where take over, regroup and come back after a few years.
The only to defeat them is to coordinate with each other, so everyone knows what's going on and they can't run off to the next tuulo.
For your information, Cayr have always had a big presence in Alshabab with many of their leaders being Cayr. While Murusade would rather be under Alshabab so they don't lose land to other qabils, than actually fight them.