Watch, getting shilling admission (6)
I believe the answer is:
sentry
'watch' is the definition.
('sentry' can be a synonym of 'watch')
'shilling admission' is the wordplay.
'shilling' becomes 's'.
'admission' becomes 'entry' (I've seen this before).
's'+'entry'='SENTRY'
'getting' acts as a link.
(Other definitions for sentry that I've seen before include "Soldier on guard" , "Sentinel, watch" , "Look-out, guard" , "Lookout soldier" , "Person posted to keep watch for some anticipated event" .)