Regret having broken mantle (6)
I believe the answer is:
lament
'regret' is the definition.
(synonyms)
'broken mantle' is the wordplay.
'broken' is an anagram indicator.
'mantle' anagrammed gives 'LAMENT'.
'having' acts as a link.
(Other definitions for lament that I've seen before include "Mourn, grieve for" , "Complain" , "Song of sorrow" , "complaint" , "requiem" .)