Rows hard: vessel is to catch good fish (5,5)
I believe the answer is:
tiger shark
'fish' is the definition.
(tiger shark is a kind of fish)
'rows hard vessel is to catch good' is the wordplay.
'rows' becomes 'tiers' (tier is a kind of row).
'hard vessel' becomes 'hark' (I can't justify this - if you can you should believe this answer much more).
'is to catch' means one lot of letters goes inside another.
'good' becomes 'g' (abbreviation).
'tiers'+'hark'='tiershark'
'tiershark' enclosing 'g' is 'TIGER-SHARK'.
Can you help me to learn more?
(Other definitions for tiger shark that I've seen before include "Large aggressive fish" , "big fish" .)