Inconsistent, sporadic (6)
I believe the answer is:
patchy
I believe this clue is a double definition.
'inconsistent' is the first definition.
(I've seen this in another clue)
'sporadic' is the second definition.
(I've seen this before)
(Other definitions for patchy that I've seen before include "Irregular in quality" , "Morose" , "Inconsistent" , "Uneven in quality; showing signs of repair" , "Intermittent" .)