Oscar intercepts letter with a counterfeit permit (8)
I believe the answer is:
tolerate
'permit' is the definition.
(I know that permit can be written as tolerate)
'oscar intercepts letter with a counterfeit' is the wordplay.
'oscar' becomes 'O' (phonetic alphabet: alpha, bravo, charlie etc.).
'intercepts' is an insertion indicator (I've seen this in other clues).
'with' says to put letters next to each other.
'counterfeit' is an anagram indicator.
'letter' after 'a' is 'aletter'.
'aletter' is an anagram of 'tlerate'.
'o' put inside 'tlerate' is 'TOLERATE'.
(Other definitions for tolerate that I've seen before include "Treat fairly" , "Allow" , "Stomach" , "Put up with, permit without protest" , "Suffer" .)