Scattered, irregular (8)
I believe the answer is:
sporadic
This clue is a double definition.
'scattered' is the first definition.
(similar in meaning)
'irregular' is the second definition.
(similar in meaning)
(Other definitions for sporadic that I've seen before include "Occurring here and there, scattered" , "Occurring at irregular intervals" , "Picadors being scattered, here and there" , "infrequent" , "Scattered - irregular" .)