Artist put in the box Irish cross (8)
I believe the answer is:
traverse
'cross' is the definition.
('traverse' can be a synonym of 'cross')
'artist put in the box irish' is the wordplay.
'artist' becomes 'ra' (Royal Academician, member of Royal Academy of Arts).
'put in' indicates putting letters inside.
'the box' becomes 'tv'.
'irish' becomes 'erse' (I've seen this before).
'ra' going inside 'tv' is 'trav'.
'trav'+'erse'='TRAVERSE'
(Other definitions for traverse that I've seen before include "Ski diagonally across (a slope)" , "cover" , "In mountaineering, a steep slope to be crossed from side to side" , "Extend or bridge across" , "get across" .)