Great achievement of one in top hotel (7)
I believe the answer is:
triumph
'great achievement' is the definition.
'triumph' can be an answer for 'achievement' (I have seen 'Notable achievement' mean 'triumph' so perhaps 'achievement' could also mean 'triumph'). I am not certain of the 'great' bit.
'one in top hotel' is the wordplay.
'one' becomes 'i' (Roman numeral).
'in' is an insertion indicator.
'top' becomes 'trump' (both can mean to beat or outdo).
'hotel' becomes 'h' (phonetic alphabet).
'i' put into 'trump' is 'triump'.
'triump'+'h'='TRIUMPH'
'of' is the link.
Can you help me to learn more?
(Other definitions for triumph that I've seen before include "Exultant victory" , "Crow" , "Successful ending of a struggle or contest" , "beat the opposition!" , "Victory, great success" .)