Having a part in something can mean being involved or playing a role in it. Some synonyms for this expression could be to take part in, contribute to, participate in, share in, play a role in, be involved in, or have a share in. These all convey the idea of having some degree of involvement or responsibility in a particular situation or project. It could also be expressed as having a hand in, or being instrumental in, which suggests that someone played a significant role in bringing about a particular outcome. Regardless of the phrasing, having a part in something implies an active involvement or contribution in some way.