Mournful and downright unimaginative quartet finale (9)
I believe the answer is:
plaintive
'mournful' is the definition.
(I know that mournful can be written as plaintive)
'and downright unimaginative quartet finale' is the wordplay.
I cannot really see how this works, but
'and' could be 'n' (common abbreviation for 'and') and 'n' is located in the answer.
'quartet' could be 'iv' (Roman numerals for four) and 'iv' is present in the answer.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for plaintive that I've seen before include "Pathetic" , "Doleful" , "Maybe weeping" , "Sounding sad and mournful" , "Wistful" .)