Unpleasant debts after broadcast on box (9)
I believe the answer is:
obnoxious
'unpleasant' is the definition.
(synonyms)
'debts after broadcast on box' is the wordplay.
'debts' becomes 'IOUs' (promises to pay debts).
'after' says to put letters next to each other.
'broadcast' indicates an anagram (letters scattered or cast around).
'on'+'box'='onbox'
'onbox' anagrammed gives 'obnox'.
'ious' put after 'obnox' is 'OBNOXIOUS'.
(Other definitions for obnoxious that I've seen before include "Nasty" , "Extremely unpleasant" , "Foul" , "Seriously disliked" , "Repugnant" .)