Sign left ten disturbed (7)
I believe the answer is:
portent
'sign' is the definition.
(portent is a kind of sign)
'left ten disturbed' is the wordplay.
'left' becomes 'port' (left side of a ship - opposite of starboard**).
'disturbed' is an anagram indicator.
'ten' with letters rearranged gives 'ent'.
'port'+'ent'='PORTENT'
(Other definitions for portent that I've seen before include "Evil omen" , "Sign, omen" , "Augury" , "Sign of thing to come" , "Warning of momentous event" .)