Brexit, primarily, is hard work for a senior minister (6)
I believe the answer is:
bishop
'a senior minister' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe you can see a link between them that I don't see?
'brexit primarily is hard work' is the wordplay.
'primarily' says to take the initial letters.
'hard' becomes 'h'.
'work' becomes 'op' (abbreviation for opus).
The first letter of 'brexit' is 'b'.
'b'+'is'+'h'+'op'='BISHOP'
'for' is the link.
Can you help me to learn more?
(Other definitions for bishop that I've seen before include "See man at the top" , "Diocesan" , "Senior churchman" , "High-ranking clergyman" , "Man of the church (or chess?)" .)