Person suggested labourer on Irish ship would treat it roughly (9)
I believe the answer is:
manhandle
'irish ship would treat it roughly' is the definition.
I can't tell whether this defines the answer.
'person suggested labourer' is the wordplay.
'person' becomes 'man' (man is a kind of person).
'suggested labourer' becomes 'handle' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'man'+'handle'='MANHANDLE'
'on' is the link.
Can you help me to learn more?
(Other definitions for manhandle that I've seen before include "Mistreat" , "Push (someone) about roughly" , "Treat roughly, or move by human effort alone" , "Give rough treatment to" , "Knock around" .)