Possibly keen to do this vocally? (5)
I believe the answer is:
mourn
'possibly keen' is the definition.
'mourn' can be an answer for 'keen' (I've seen this in another clue). I'm not sure about the 'possibly' bit.
I don't understand how the remainder of the clue works.
(Other definitions for mourn that I've seen before include "Keen" , "Show sorrow for loss" , "Regret (a loss)" , "Weep for" , "Express sadness" .)