Titanic could end in tragedy (6)
I believe the answer is:
mighty
'titanic' is the definition.
(thesaurus)
'could end in tragedy' is the wordplay.
'could' becomes 'might' (synonyms).
'end in' suggests the final letters.
The last letter of 'tragedy' is 'y'.
'might'+'y'='MIGHTY'
(Other definitions for mighty that I've seen before include "Arrogant people are often described as high and . . . . . ." , "Strong, powerful" , "Having great strength" , "Very powerful/strong" , "Powerful - huge" .)