Sadly, son, I can't give permission (8)
I believe the answer is:
sanction
'give permission' is the definition.
(thesaurus)
'sadly son i can't' is the wordplay.
'sadly' indicates an anagram.
'son'+'i'+'cant'='sonicant'
'sonicant' is an anagram of 'SANCTION'.
(Other definitions for sanction that I've seen before include "Allow; punish" , "Permission or approval as for course of action" , "Authorisation" , "Confirm" , "Give approval to, authorise" .)