Shameless for sure, men breaking heart of fraulein (12)
I believe the answer is:
unremorseful
'shameless' is the definition.
(having no shame or remorse)
'for sure men breaking heart of fraulein' is the wordplay.
'breaking' indicates anagramming the letters.
'heart of' says to take the centre.
The central letters of 'fraulein' are 'ul'.
'for'+'sure'+'men'='forsuremen'
'forsuremen' anagrammed gives 'unremorsef'.
'unremorsef'+'ul'='UNREMORSEFUL'
(Other definitions for unremorseful that I've seen before include "Impenitent" , "Showing no regret" .)