Slow to act; tardy (8)
I believe the answer is:
dilatory
I believe this clue is a double definition.
'slow to act' is the first definition.
(I've seen this before)
'tardy' is the second definition.
(I've seen this in another clue)
(Other definitions for dilatory that I've seen before include "Inclined to dawdle" , "Slothful in idolatry" , "Causing delay" , "Delaying" , "Given to procrastination" .)