Fitful, intermittent (8)
I believe the answer is:
sporadic
I believe this clue is a double definition.
'fitful' is the first definition.
(similar in meaning)
'intermittent' is the second definition.
(similar in meaning)
(Other definitions for sporadic that I've seen before include "Occurring at irregular intervals" , "Occurring here and there, scattered" , "Scattered - irregular" , "Occurring here and there, like picadors" , "Random" .)