Choose to make U-turn, concealing company’s last mistake (4)
I believe the answer is:
typo
'mistake' is the definition.
(typographical error)
'choose to make u-turn concealing company's last' is the wordplay.
'choose' becomes 'opt' (both can mean to pick something).
'to make u-turn' says the letters should be written backwards.
'concealing' indicates putting letters inside.
'last' indicates one should take the final letters.
The final letter of 'company' is 'y'.
'opt' backwards is 'tpo'.
'tpo' enclosing 'y' is 'TYPO'.
(Other definitions for typo that I've seen before include "Literal error in printed matter, in short" , "Small keyboarding error" , "Spelling mistake" , "False character" , "Printer's error" .)