Brit's undershirt (4)
I believe the answer is:
vest
'brit's undershirt' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for vest that I've seen before include "Undergarment for upper body" , "Sleeveless undergarment" , "Waistcoat (in USA)" , "Undergarment for vets" , "Undershirt, singlet" .)