Passage in a play ultimately showing indifference (6)
I believe the answer is:
apathy
'indifference' is the definition.
('apathy' can be a synonym of 'indifference')
'passage in a play ultimately' is the wordplay.
'passage' becomes 'path' (I've seen this in other clues**).
'in' is an insertion indicator.
'ultimately' indicates one should take the final letters.
The last letter of 'play' is 'y'.
'a'+'y'='ay'
'path' put into 'ay' is 'APATHY'.
'showing' acts as a link.
(Other definitions for apathy that I've seen before include "Torpor" , "Lack of interest or concern" , "lack of involvement" , "Absense of interest or emotion" , "Absence of emotion or enthusiasm" .)