This writer's adopting old airline's screen symbol (1-4)
I believe the answer is:
i-beam
'screen symbol' is the definition.
(I-shaped computer cursor)
'this writer's adopting old airline's' is the wordplay.
'this writer's' becomes 'im' (the person writing the crossword clues).
'adopting' indicates putting letters inside.
'old airline' becomes 'bea' (British European Airways).
'im' placed around 'bea' is 'I-BEAM'.
(Other definitions for i-beam that I've seen before include "Metal girder I-shaped in cross-section" , "Rigid metal girder" , "Structural girder" , "Common type of metal girder" .)