Councillor at work with a coterie sees a phenomenon of unexplained origin (4,6)
I believe the answer is:
crop circle
'a phenomenon of unexplained origin' is the definition.
I don't know anything about this answer so I can't judge whether this works.
'councillor at work with a coterie' is the wordplay.
'councillor' becomes 'cr' (abbreviation).
'at' is a charade indicator (letters next to each other).
'work' becomes 'op' (short for opus).
'with' is a charade indicator (letters next to each other).
'a coterie' becomes 'circle' (I've seen this in another clue).
'cr'+'op'+'circle'='CROP CIRCLE'
'sees' acts as a link.
Can you help me to learn more?
(Other definitions for crop circle that I've seen before include "Hertfordshire new town" , "mysterious country area" .)