Fellow Irishman in charge of the organ (7)
I believe the answer is:
hepatic
'fellow irishman in charge of the organ' is the definition.
I can't judge whether this definition defines the answer.
'fellow irishman in charge of' is the wordplay.
'fellow' becomes 'he' ('he' refers to a man).
'irishman' becomes 'Pat' (Patrick is a common Irish name).
'in charge of' becomes 'ic'.
'he'+'pat'+'ic'='HEPATIC'
Can you help me to learn more?
(Other definitions for hepatic that I've seen before include "of an organ" , "Pertaining to, or affecting, the liver or liverwort" , "Relating to the liver" , "Livery" , "brownish-red" .)