Surveillance post exposed (8)
I believe the answer is:
stakeout
'surveillance' is the definition.
(stakeout is a kind of surveillance)
'post exposed' is the wordplay.
'post' becomes 'stake' ('stake' can be a synonym of 'post').
'exposed' becomes 'out' (I've seen this in other clues).
'stake'+'out'='STAKEOUT'
(Other definitions for stakeout that I've seen before include "Informally, place under surveillance - using sharp stick?" , "Act of surveillance" , "watch closely" , "Put under surveillance - like statue, OK?" , "Secret surveillance by police" .)