He’s back from going round N Ireland (5)
I believe the answer is:
ernie
'he's' is the definition.
'back from going round n ireland' is the wordplay.
'back' says the letters should be written backwards.
'from' becomes 'e' (I've seen this in other clues).
'going round' means one lot of letters goes inside another (some letters go around others).
'ireland' becomes 'ire' (abbreviation).
'n' placed inside 'ire' is 'inre'.
'e'+'inre'='einre'
'einre' written backwards gives 'ERNIE'.
(Other definitions for ernie that I've seen before include "Selector of winning premium bond numbers" , "It picks Premium Bond winners" , "Guy" , "Wise fellow" , "Els, for example" .)