Large vessel: fish nets I say on one (5,4)
I believe the answer is:
cargo ship
'large vessel' is the definition.
'cargo ship' can be an answer for 'vessel' (cargo ship is a kind of vessel). I'm not certain of the 'large' bit.
'fish nets i say on one' is the wordplay.
'fish' becomes 'carp' (carp is a kind of fish).
'nets' is an insertion indicator (some letters are contained or netted).
'i say' becomes 'gosh' (both are expressions of surprise).
'on' says to put letters next to each other.
'one' becomes 'i' (Roman numeral).
'gosh'+'i'='goshi'
'carp' placed around 'goshi' is 'CARGO SHIP'.
Can you help me to learn more?
(Another definition for cargo ship that I've seen is " vessel".)