Unpredictable (7)
I believe the answer is:
erratic
'unpredictable' is the definition.
(synonyms)
This is the entire clue.
(Other definitions for erratic that I've seen before include "Irregular, capricious" , "Irregular or uneven in movement or habits" , "Sporadic" , "Irregular and unpredictable" , "Deep affection" .)