Jack: Irishman round in the morning (6)
I believe the answer is:
seaman
'jack' is the definition.
(I know that jack can be written as seaman)
'irishman round in the morning' is the wordplay.
'irishman' becomes 'sean' (common Irish name).
'round' indicates putting letters inside.
'in the morning' becomes 'am' (AM on a clock).
'sean' going around 'am' is 'SEAMAN'.
(Other definitions for seaman that I've seen before include "A manse (anag.)" , "Sailor" , "crew member" , "Mariner" .)