keep hand in
keep (one's) hand in (something)
1. To remain involved in something, often in a minor role or capacity. Joe insists on keeping his hand in the company, even though he has no real authority at this point.
2. To continue to do something in order to maintain a particular skill or ability. I've mostly stopped acting, but I will do a play occasionally, just to keep my hand in.
keep one's hand in (something)
Fig. to remain involved in something, perhaps only a token involvement. I want to keep my hand in things even after I retire. I always have to keep my hand in so I will feel a part of things.