But commonly reduced (4)
I believe the answer is:
only
'but' is the definition.
(I've seen this in another clue)
'commonly reduced' is the wordplay.
'ONLY' is hidden in amongst the letters.
But, I'm uncertain how this is indicated.
Can you help me to learn more?
(Other definitions for only that I've seen before include "Simply" , "Alone; solitary" , "And no one else" , "Solely; except that" , "Unique; merely" .)