Permit, or punitively deter, second name appearing in deed (8)
I believe the answer is:
sanction
'permit' is the definition.
(I know that sanction is a more specific form of the action O.K.)
'second name appearing in deed' is the wordplay.
'second' becomes 's' (common abbreviation).
'name' becomes 'n' (common abbreviation e.g. on forms).
'appearing in' means one lot of letters goes inside another.
'deed' becomes 'action' (I've seen this before).
'n' placed inside 'action' is 'anction'.
's'+'anction'='SANCTION'
'or punitively deter' is the link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for sanction that I've seen before include "Confirm" , "Penalty for breaking law" , "Allow; punish" , "Threatened penalty; official permission" , "measure taken against offending country?" .)