Detailed account mountaineer fabricated (11)
I believe the answer is:
enumeration
'detailed account' is the definition.
'enumeration' can be an answer for 'account' (thesaurus). I am not sure about the 'detailed' bit.
'mountaineer fabricated' is the wordplay.
'fabricated' indicates anagramming the letters.
'mountaineer' with letters rearranged gives 'ENUMERATION'.
Can you help me to learn more?
(Other definitions for enumeration that I've seen before include "Counting process" , "The act of mentioning one by one" , "The act of numbering" , "Act of counting" .)