Polish hotel's dated exterior (5)
I believe the answer is:
sheen
'polish' is the definition.
(both can mean a shiny surface)
'hotel's dated exterior' is the wordplay.
'hotel' becomes 'h' (phonetic alphabet: alpha, bravo, charlie etc.).
'dated' becomes 'seen' (I've seen this in another clue).
'exterior' indicates putting letters inside (some letters go on the outside of others).
'h' placed into 'seen' is 'SHEEN'.
(Other definitions for sheen that I've seen before include "Soft lustre on a surface" , "Surface gloss" , "Superficial brightness" , "Radiance" , "place in London" .)