Work in charge of persuasion (7)
I believe the answer is:
opinion
'persuasion' is the definition.
(I know that persuasion can be written as opinion)
'work in charge' is the wordplay.
'work' becomes 'op' (short for opus).
'charge' becomes 'ion' (an ion is a charged particle).
'op'+'in'+'ion'='OPINION'
'of' is the link.
(Other definitions for opinion that I've seen before include "Belief or conviction" , "View held without positive proof" , "Assessment" , "Viewpoint" , "Personal belief or judgment" .)