Bomb shelter descended on by US politicians (2,4)

I believe the answer is:

go phut

'bomb' is the definition.
(both can mean to fail to work)

'shelter descended on by us politicians' is the wordplay.
'shelter' becomes 'hut' (hut is a kind of shelter).
'descended on by' is a charade indicator (letters next to each other) (in a down clue, some letters descend onto others).
'us politicians' becomes 'GOP' (the Grand Old Party, nickname for US Republicans).
'hut' after 'gop' is 'GO PHUT'.

(Another definition for go phut that I've seen is " fail".)

I've seen this clue in The Times.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.