The poem we hear, was outstanding (4)
I believe the answer is:
owed
'was outstanding' is the definition.
(I've seen this in another clue)
'the poem we hear' is the wordplay.
'the poem' becomes 'ode' (ode is a kind of poem).
'we hear' shows a homophone (sound like).
'ode' is a homophone of 'OWED'.
(Other definitions for owed that I've seen before include "Had a duty to pay" , "Had an obligation to pay" , "Was obliged to pay" , "Outstanding" , "In debt to" .)