An Outlook glitch in terminals makes Egyptian cross (4)
I believe the answer is:
ankh
'egyptian cross' is the definition.
(I've seen this before)
'an outlook glitch in terminals makes' is the wordplay.
'an' becomes 'a'.
'terminals' suggests the final letters (I've seen 'terminal' mean this (terminal refers to the end)).
'makes' indicates an anagram.
The last letters of 'outlook glitch in' are 'khn'.
'khn' with letters rearranged gives 'nkh'.
'a'+'nkh'='ANKH'
(Other definitions for ankh that I've seen before include "Ansate cross" , "Egyptian hieroglyph representing life" , "Egyptian cross" , "Cross with a loop at the top, symbol of life in ancient Egypt" , "Hank (anag) - cross symbolising eternal life" .)