Clue: I produce something you can rattle up and down in a box (7)
Answer: CHEMIST
Explanation: Definition: I produce something you can rattle up and down in a box
**HEM** ("something you can rattle up and down") *in* **CIST** ("box") and &lit. 
 
 
*I have a faint recollection that "rattle up a hem" is a phrase, but I may be misremembering?