Point at the gate for the guard (6)
I believe the answer is:
sentry
'the guard' is the definition.
(sentry is a kind of guard)
'point at the gate' is the wordplay.
'point' becomes 'S' (S is an example).
'at' means one lot of letters go next to another.
'the gate' becomes 'entry' (I've seen this in another clue).
's'+'entry'='SENTRY'
'for' acts as a link.
(Other definitions for sentry that I've seen before include "Soldier posted to keep watch" , "One keeps watch" , "One keeps guard" , "Mil. guard" , "Watchperson" .)