### Clue: Dividing wall takes a month? I'm not sure (6)
### Answer: SEPTUM 
 ### Explanation: Definition: Dividing wall
 SEPT(short for the 9th month of the year) + UM(an expression of uncertainty;"I'm not sure").
Defn: …, or membrane between 2 cavities in an organism's body, eg. that between the left and right nostrils.