Attempt to conceal old catastrophe (7)
I believe the answer is:
tragedy
'catastrophe' is the definition.
(synonyms)
'attempt to conceal old' is the wordplay.
'attempt to' becomes 'try' (I've seen this in other clues).
'conceal' means one lot of letters goes inside another.
'old' becomes 'aged' (similar in meaning).
'try' going around 'aged' is 'TRAGEDY'.
(Other definitions for tragedy that I've seen before include "Huge blow" , "Calamity, disaster" , "literary genre Aristotle analysed" , "Drama genre" , "Serious catastrophe" .)