have a hand in

have or keep one's hand in . Be actively engaged or remain in practice doing something. For example, He works as stage manager, director, understudy—he has a hand in every aspect , or Write a few pages every day, just to keep your hand in . [Mid-1700s]

Also, take a hand in . Participate, be involved, as in I'd like to have a hand in planning the publicity . [Late 1500s]