Quick joke about eastern ship (3-5)
I believe the answer is:
one-liner
'quick joke' is the definition.
(I've seen this before)
'about eastern ship' is the subsidiary indication.
'about' becomes 'on' (**).
'eastern' becomes 'e'.
'ship' becomes 'liner' (liner is a kind of ship).
'on'+'e'+'liner'='oneliner'
(Other definitions for one-liner that I've seen before include "Witty remark contained in a single sentence" , "Pithy joke" , "Flat, smooth" , "Single sentence jokes" , "Quick joke?" .)