Topless undergarment on girl lifted bust (4)
I believe the answer is:
raid
'bust' is the definition.
(I've seen this before)
'topless undergarment on girl lifted' is the wordplay.
'topless' means to remove the first letter.
'undergarment' becomes 'bra' (I've seen this before).
'on' is a charade indicator (letters next to each other).
'girl' becomes 'di' (**).
'lifted' says the letters should be written in reverse (going up in down clue).
'di' back-to-front is 'id'.
'bra' with its initial letter removed is 'ra'.
'ra'+'id'='RAID'
(Other definitions for raid that I've seen before include "Rifle" , "Sudden short attack" , "Finch and Bronson starred in . . . . On Entebbe" , "Assault, attack" , "Inroad" .)