Crop said to be intermittent (8)
I believe the answer is:
sporadic
'intermittent' is the definition.
(similar in meaning)
'crop said to be' is the wordplay.
'to be' indicates anagramming the letters.
'crop'+'said'='cropsaid'
'cropsaid' anagrammed gives 'SPORADIC'.
(Other definitions for sporadic that I've seen before include "Having separate patches" , "Picadors being scattered, here and there" , "Isolated; intermittent" , "Happening irregularly" , "Occurring here and there, like picadors" .)