Crossword Genius

Endlessly regretting destruction (4)

Ross

I believe the answer is:

ruin

Here is my best explanation:

'destruction' is the definition.
(ruin is a kind of destruction)

'endlessly regretting' is the wordplay.
'endlessly' means to remove the last letter.
'regretting' becomes 'ruing' ('rue' can be a synonym of 'regret').
'ruing' with its final letter taken off is 'RUIN'.

This clue was last seen in Mirror