just to shake a leg

[Michael_cycle]

The crowds waited outside Mumbai's MMRDA grounds more than just to shake a leg.

In her first ever concert in India, Latin singer and performer Shakira got a 20,000 strong audience grooving to her tunes.

Please explain the highlighted group of words.

 

[Siberia]

Shake a leg is an idiom and it just means wake up, hurry up - literally -
Rouse yourself from sleep and get out of bed.
Grovving to her tunes - dancing, moving to her music.