One man holds power to transfix.. (6)
I believe the answer is:
impale
'to transfix' is the definition.
(synonyms)
'one man holds power' is the wordplay.
'one' becomes 'i' (Roman numeral).
'man' becomes 'male' ().
'holds' is an insertion indicator.
'power' becomes 'p' (symbol in physics).
'male' enclosing 'p' is 'mpale'.
'i'+'mpale'='IMPALE'
(Other definitions for impale that I've seen before include "Puncture" , "Pierce through as with sharp stick" , "Kill by piercing with a spear or sharp pole" , "Pierce, me pail (anag.)" , "transfix with sharp item" .)