Former buccaneer loses right to do penance (7)
I believe the answer is:
expiate
'do penance' is the definition.
(thesaurus)
'former buccaneer loses right' is the wordplay.
'former' becomes 'ex'.
'buccaneer' becomes 'pirate' ('pirate' can be a synonym of 'buccaneer').
'loses' suggests deleting specific letters.
'right' becomes 'r' (common abbreviation).
'pirate' with 'r' taken away is 'piate'.
'ex'+'piate'='EXPIATE'
'to' acts as a link.
(Other definitions for expiate that I've seen before include "make atonement" , "Pay for" , "Make amends for wrongdoing" , "Atone for (a sin)" , "Of sin, make amends for" .)