Outstanding poem we hear? (4)
I believe the answer is:
owed
'outstanding' is the definition.
(as in an outstanding debt)
'poem we hear?' is the wordplay.
'poem' becomes 'ode' (ode is a type of poem).
'we hear?' shows a homophone (sound like).
'ode' sounds like 'OWED'.
(Other definitions for owed that I've seen before include "Was indebted" , "Was due to pay" , "Was obliged to pay" , "to be paid" , "Had a duty to pay" .)