Terrible funeral song not good (4)
I believe the answer is:
dire
'terrible' is the definition.
(synonyms)
'funeral song not good' is the wordplay.
'funeral song' becomes 'dirge' (I've seen this in another clue).
'not' is a deletion indicator.
'good' becomes 'g' (abbreviation).
'dirge' with 'g' removed is 'DIRE'.
(Other definitions for dire that I've seen before include "Very serious indeed" , "Really dreadful - ride on" , "Of very poor quality" , "Terrible display" , "Terrible; urgent" .)