Unemployed debt-collector bitten by ruddy insect! (9)
I believe the answer is:
redundant
'unemployed' is the definition.
'debt-collector bitten by ruddy insect' is the wordplay.
'debt collector' becomes 'dun' (I've seen this in other clues).
'bitten by' means one lot of letters goes inside another (I've seen this in other clues).
'ruddy' becomes 'red' (synonyms).
'insect' becomes 'ant' (ant is a kind of insect).
'dun' put within 'red' is 'redund'.
'redund'+'ant'='REDUNDANT'
(Other definitions for redundant that I've seen before include "no longer needed" , "out of a job" , "No longer necessary" , "getting P45?" , "No longer required, unnecessary" .)