Possibly tedious letter from Penzance (7)
I believe the answer is:
penance
'possibly tedious' is the definition.
I can't tell whether this defines the answer.
'letter from penzance' is the wordplay.
'letter' becomes 'z'.
'from' suggests deleting specific letters.
'penzance' with 'z' taken away is 'PENANCE'.
Can you help me to learn more?
(Other definitions for penance that I've seen before include "Act of atonement" , "Act performed in sorrow for sin" , "Expression of sorrow for sin" , "Act of penitence" , "Voluntary self-punishment" .)