New word energy in ol’ Mog’s anagrams (9)
I believe the answer is:
neologism
'new word' is the definition.
(thesaurus)
'energy in ol' mog's anagrams' is the wordplay.
'energy' becomes 'e' (physics symbol as in E=mc2).
'anagrams' is an anagram indicator (I've seen 'anagram of' mean this).
'e'+'in'+'ol'+'mogs'='einolmogs'
'einolmogs' anagrammed gives 'NEOLOGISM'.
(Other definitions for neologism that I've seen before include "Newly-coined word or expression" , "Brexit maybe" , "coinage" , "new term" , "Newly coined word" .)