Hotel in Donegal rebuilt hastily (8)
I believe the answer is:
headlong
'hastily' is the definition.
(thesaurus)
'hotel in donegal rebuilt' is the wordplay.
I cannot quite see how this works, but
'hotel' could be 'h' (phonetic alphabet: alpha, bravo, charlie etc.) and 'h' is found within the answer.
an anagram of 'donegal' is 'eadlong' which is present in the answer.
No letters remain.
This may be the basis of the clue (or it may be nonsense).
(Other definitions for headlong that I've seen before include "work by 3 [FRAYN] > at full speed" , "Recklessly" , "Quickly" , "Let handle go in manner of falling" , "In hasty or plunging manner" .)