Sound of birds warbling outside hotel that’s exciting (6)
I believe the answer is:
thrill
'that's exciting' is the definition.
(a thrill is something exciting)
'sound of birds warbling outside hotel' is the wordplay.
'sound of birds warbling' becomes 'trill' (sound made by a bird).
'outside' is an insertion indicator.
'hotel' becomes 'h' (phonetic alphabet).
'trill' placed around 'h' is 'THRILL'.
(Other definitions for thrill that I've seen before include "Sudden rush of pleasure" , "Almost pleasurable sensation of fright" , "gas" , "Shudder of excitement" , "Exhilarate, excite" .)