Show lack of interest in Irish rugby (5)
I believe the answer is:
shrug
'show lack of interest' is the definition.
(a shrug indicates a lack of interest)
'in irish rugby' is the wordplay.
'in' indicates the answer is hidden within the clue.
'SHRUG' is hidden in the letters of 'irish rugby'.
(Other definitions for shrug that I've seen before include "Show lack of concern" , "Expressive shoulder movement" , "Indifferent gesture" , "Raise one's shoulders" , "Affect indifference" .)