Small admission by one of those at The Gate (6)
I believe the answer is:
sentry
'one of those at the gate' is the definition.
I can't judge whether this definition defines the answer.
'small admission by' is the wordplay.
'small' becomes 's' (abbreviation - e.g. clothes size).
'admission' becomes 'entry' (I've seen this before).
'by' says to put letters next to each other.
's'+'entry'='SENTRY'
Can you help me to learn more?
(Other definitions for sentry that I've seen before include "Lookout person" , "Person standing watch" , "Military lookout" , "Lookout soldier" , "Watchman" .)