Chief found target a nonstarter and left worker (9)
I believe the answer is:
important
'chief' is the definition.
(similar in meaning)
'target a nonstarter and left worker' is the wordplay.
'target a nonstarter' becomes 'im' (I am not sure about this - if you are sure you should believe this answer much more).
'and' is a charade indicator (letters next to each other).
'left' becomes 'port' (left side of a ship - opposite of starboard).
'worker' becomes 'ant' (worker is a type of ant).
'im'+'port'+'ant'='IMPORTANT'
'found' acts as a link.
Can you help me to learn more?
(Other definitions for important that I've seen before include "Noted" , "Historic" , "Of significance or value" , "major" , "A priority" .)