Does try badly to ruin (7)
'ruin' is the definition.
('destroy' can be a synonym of 'ruin')
'does try badly' is the wordplay.
'badly' is an anagram indicator.
'doestry' anagrammed gives 'DESTROY'.
'to' acts as a link.
(Other definitions for destroy that I've seen before include "put to death", "Annihilate", "Get rid of", "Flatten", "Demolish; pull down".)