Soviet agency netting a thousand in duties (5)
I believe the answer is:
tasks
'duties' is the definition.
(task is a kind of duty)
'soviet agency netting a thousand' is the wordplay.
'soviet agency' becomes 'tass' (I've seen this in another clue).
'netting' is an insertion indicator (net can mean to contain or capture).
'a thousand' becomes 'K' ('K' can be a synonym of 'thousand').
'tass' going around 'k' is 'TASKS'.
'in' acts as a link.
(Other definitions for tasks that I've seen before include "'Jobs, undertakings (5)'" , "charges" , "Chores, duties" , "Pieces of work" , "Jobs to be done" .)