Some fellow is dominating accumulated knowledge (6)
I believe the answer is:
wisdom
'accumulated knowledge' is the definition.
(I've seen this in another clue)
'some fellow is dominating' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'WISDOM' can be found hidden inside 'fellow is dominating'.
(Other definitions for wisdom that I've seen before include "writing" , "Knowledge gained through experience" , "Accumulated experience and mature judgement" , "Accumulated learning, sagacity" , "Prudence - or Norman?" .)