Wholly engrossed (4)
I believe the answer is:
rapt
'wholly engrossed' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for rapt that I've seen before include "Spellbound, enthralled" , "Part of being intent and absorbed" , "Ecstatic - engrossed" , "Spellbound in part" , "riveted" .)