Trade union cross with editor at first over formal jacket? (6)
I believe the answer is:
tuxedo
'formal jacket?' is the definition.
'trade union cross with editor at first over' is the wordplay.
'trade union' becomes 'TU' (abbreviation for trade union).
'cross' becomes 'x' (X is cross-shaped).
'with' says to put letters next to each other.
'editor' becomes 'ed' (abbreviation).
'at first' indicates taking the first letters.
The initial letter of 'over' is 'o'.
'tu'+'x'+'ed'+'o'='TUXEDO'
(Other definitions for tuxedo that I've seen before include "American dinner jacket" , "Dinner jacket (US)" , "An American monkey-suit" , "Garment" , "American DJ" .)