US police officer alarms suspect outside hotel (7)
I believe the answer is:
marshal
'us police officer' is the definition.
(type of US police officer)
'alarms suspect outside hotel' is the wordplay.
'suspect' indicates anagramming the letters (a suspicious or unusual spelling).
'outside' indicates putting letters inside.
'hotel' becomes 'h' (phonetic alphabet: alpha, bravo, charlie etc.).
'alarms' with letters rearranged gives 'marsal'.
'marsal' placed around 'h' is 'MARSHAL'.
(Other definitions for marshal that I've seen before include "Shepherd" , "High officer" , "Sports event official" , "US federal officer" , "High-ranking officer" .)