Let in as a concession? (5)
I believe the answer is:
admit
'let in' is the definition.
(synonyms)
I don't understand the remainder of the clue.
Can you help me to learn more?
(Other definitions for admit that I've seen before include "Agree to the truth" , "Take on" , "Profess" , "Reveal" , "Confess; allow in" .)