Perform either part of a duet in prison (4)
I believe the answer is:
sing
'perform' is the definition.
(to perform a song)
'either part of a duet in prison' is the wordplay.
I cannot quite understand how this works, but
'part' could be 'si' (si is a kind of part) and 'si' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for sing that I've seen before include "Warble" , "Turn informer" , "pipe" , "Inform - carol" , "Make melodious sounds with voice" .)