Paid in post but badly let down (10)
I believe the answer is:
disappoint
'let down' is the definition.
(I know that let down can be written as disappoint)
'paid in post but badly' is the wordplay.
'paid in post' anagrams to 'DISAPPOINT'.
However, I'm not sure how this is indicated.
Can you help me to learn more?
(Other definitions for disappoint that I've seen before include "Fail to satisfy" , "Let down" .)