Heading off scoundrel US campus let in (5)
I believe the answer is:
admit
'let in' is the definition.
(synonyms)
'heading off scoundrel us campus' is the wordplay.
'heading off' means to remove the first letter.
'scoundrel' becomes 'cad' (cad is a kind of scoundrel).
'us campus' becomes 'mit' (I am not sure about this - if you are sure you should believe this answer much more).
'cad' with its first letter taken off is 'ad'.
'ad'+'mit'='ADMIT'
Can you help me to learn more?
(Other definitions for admit that I've seen before include "Confess (to something)" , "Confess - let in" , "Stop being obstructive" , "Fess up" , "Confess; allow in" .)