Appearance not acceptable for person keeping watch (7)
I believe the answer is:
lookout
'person keeping watch' is the definition.
(I've seen this before)
'appearance not acceptable' is the wordplay.
'appearance' becomes 'look' (look is a kind of appearance).
'not acceptable' becomes 'out' (cricket term).
'look'+'out'='LOOKOUT'
'for' is the link.
(Other definitions for lookout that I've seen before include "A sentry or guard, must be watchful" , "Observation point" , "Person keeping watch" , "Beware - keep a sharp eye open" , "Be careful!" .)