improver

1. Something that, or someone who, improves something.

2. One who improves his or her performance, one who shows improvement (of individuals or groups).

3. A substance added to cause improvement (especially to a foodstuff).

4. (historical)A pad worn by women to make the dress hang properly.

5. One who performs improv; an improviser.

6. (obsolete)Specifically, a person who improves land or property, a landscaper.

regular