Avoid one working at important task (7)
I believe the answer is:
mission
'task' is the definition.
(I've seen this in another clue)
'avoid one working at important' is the wordplay.
'avoid' becomes 'miss' (miss can mean to avoid).
'one working' becomes 'on' (on can mean working or activated).
'at' means one lot of letters go next to another (I've seen this in other clues).
'important' becomes 'i' (this might be a standard abbreviation which I don't know about).
'on' after 'i' is 'ion'.
'miss'+'ion'='MISSION'
Can you help me to learn more?
(Other definitions for mission that I've seen before include "1996 Tom Cruise spy film -- extremely dangerous assignment" , "In religious campaign" , "Journey with a specific purpose" , "Very dangerous assignment -- Tom Cruise film series" , "Vocation; embassy" .)