Mum stops swim after Jack and I jumped in the sea (9,4)
I believe the answer is:
abandoned ship
'mum stops swim' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'jack and i jumped in the sea' is the wordplay.
'jack' becomes 'ab' (both can mean a sailor).
'i' becomes 'one' (Roman numeral for one).
'jumped' shows that the letters should be reversed in order (I've seen 'jumping' mean this (in a down clue, letters jump up)).
'in the sea' becomes 'pihsd' (I can't explain this - if you can you should believe this answer much more).
'pihsd' in reverse letter order is 'dship'.
'ab'+'and'+'one'+'dship'='ABANDONED SHIP'
'after' is the link.
Can you help me to learn more?
(Other definitions for abandoned ship that I've seen before include "left failing organisation" , "Hurriedly left an organisation or enterprise" , "Took to the lifeboats" .)