Her dire plan shattered a womaniser (11)
I believe the answer is:
philanderer
'a womaniser' is the definition.
('philanderer' can be a synonym of 'womaniser')
'her dire plan shattered' is the wordplay.
'shattered' indicates an anagram.
'her'+'dire'+'plan'='herdireplan'
'herdireplan' anagrammed gives 'PHILANDERER'.
(Other definitions for philanderer that I've seen before include "Male flirt" , "Womaniser, libertine" , "Casual lover" , "wolf" .)