Great hotel destroyed completely (10)
I believe the answer is:
altogether
'completely' is the definition.
('altogether' can be a synonym of 'completely')
'great hotel destroyed' is the wordplay.
'destroyed' indicates an anagram.
'great'+'hotel'='greathotel'
'greathotel' anagrammed gives 'ALTOGETHER'.
(Other definitions for altogether that I've seen before include "Entirely" , "nude in this" , "totally" , "Completely, on the whole" , "Quite" .)