Secretly maintain hotel's leafy area (7)
I believe the answer is:
harbour
'secretly maintain' is the definition.
'hotel's leafy area' is the wordplay.
'hotel' becomes 'h' (phonetic alphabet: alpha, bravo, charlie etc.).
'leafy area' becomes 'arbour'.
'h'+'arbour'='HARBOUR'
(Other definitions for harbour that I've seen before include "Bear" , "Place of refuge" , "Sheltered anchorage" , "Ship haven or shelter" , "Protected mooring" .)