### Clue: Brief flash in long cloud, measure dropping straight down (9)
### Answer: PLUMB LINE 
 ### Explanation: Definition: measure dropping straight down
BLIN-g="Brief flash" inside PLUME="long cloud" 
bling=flash in the sense of ostentatious style
 
*edit – Joseph Keith Morgan, Sagittarius and others in comments have pointed out BLIN-k for "Brief flash"