Don't go for a decent run! (6)
I believe the answer is:
streak
'run' is the definition.
(streaking is a kind of running)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for streak that I've seen before include "irregular line of colour" , "'Sudden flash, of lightning say (6)'" , "run risk of arrest at sporting event?" , "exposz" , "Unbroken series, of luck say" .)