Having broken the pen rest, is contrite (7)
I believe the answer is:
repents
'is contrite' is the definition.
(I've seen this in another clue)
'having broken the pen rest' is the wordplay.
'having broken' indicates an anagram.
'pen'+'rest'='penrest'
'penrest' with letters rearranged gives 'REPENTS'.
(Other definitions for repents that I've seen before include "Present (anag.)" , "Expresses sorrow for sin" , "Feels remorse for, sin perhaps" , "Turns away from evil" , "Feels sincere remorse" .)