Clue: Bad debts covered by firm; investor finally cheers up (9)
Answer: ATROCIOUS
Explanation: Definition: Bad
A charade of ATROC, a reversal ('up' in a down light) of CO ('firm') plus R ('investo**R** finally') plus TA ('cheers'); plus IOUS ('debts'), with 'covered by' indicating the order of the particles (in a down light).