Returns policy is awful and ultimately needs changing — that is accepted (6)
I believe the answer is:
yields
'returns' is the definition.
(I know this)
'policy is awful and ultimately needs changing that is accepted' is the wordplay.
'ultimately' suggests the final letters.
'needs changing' indicates an anagram (I've seen this in other clues).
'that is' becomes 'ie' (short for Latin 'id est', 'that is').
'accepted' is an insertion indicator.
The final letters of 'policy is awful and' are 'ysld'.
'ysld' is an anagram of 'ylds'.
'ylds' enclosing 'ie' is 'YIELDS'.
(Other definitions for yields that I've seen before include "Gives in to the crops" , "Investment returns" , "Submits" , "Concedes; generates" , "Surrenders like harvests" .)