Navigational craft easily performed last of tasks with it (9)
I believe the answer is:
lightship
'navigational craft' is the definition.
(boat with a light)
'easily performed last of tasks with it' is the wordplay.
'easily performed' becomes 'light' (light can mean easy to do or straightforward).
'last of' says to take the final letters.
'with it' becomes 'hip' (I've seen this before).
The final letter of 'tasks' is 's'.
'light'+'s'+'hip'='LIGHTSHIP'
(Other definitions for lightship that I've seen before include "Moored vessel warning sailors of a hazard" , "Guiding vessel sounds as if it has no cargo" , "Pilot's guide" , "Navigational aid" , "Beacon vessel at sea" .)