Yours truly on steamship causing chaos (4)
I believe the answer is:
mess
'chaos' is the definition.
(thesaurus)
'yours truly on steamship' is the wordplay.
'yours truly' becomes 'me'.
'on' says to put letters next to each other.
'steamship' becomes 'ss'.
'me'+'ss'='MESS'
'causing' acts as a link.
(Other definitions for mess that I've seen before include "An officer's untidy dining room" , "Disarray" , "State of disorder" , "Disagreeable mixture" , "Dirty or untidy state" .)