Most leap onto boat after splitting from the Titanic (5)
I believe the answer is:
jumbo
'titanic' is the definition.
(thesaurus)
'most leap onto' is the wordplay.
'most' means to remove the last letter.
'leap' becomes 'jump' (synonyms).
'onto' becomes 'bo' (I can't justify this - if you can you should give a lot more credence to this answer).
'jump' with its last letter removed is 'jum'.
'jum'+'bo'='JUMBO'
'boat after splitting from the' acts as a link.
I am not very happy about this link. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for jumbo that I've seen before include "Something very large of its kind - say a jet" , "Owner of trunk" , "Immense" , "monster" , "Large plane" .)