Attribute of one saying nothing about power (6)
I believe the answer is:
impute
'attribute' is the definition.
(I know that attribute can be written as impute)
'one saying nothing about power' is the wordplay.
'one' becomes 'i' (Roman numeral).
'saying nothing' becomes 'mute' (I've seen this in another clue).
'about' indicates putting letters inside.
'power' becomes 'p' (symbol in physics).
'mute' enclosing 'p' is 'mpute'.
'i'+'mpute'='IMPUTE'
'of' acts as a link.
(Other definitions for impute that I've seen before include "Ascribe, assign" , "Attribute (misdeed) to someone" , "reckon" , "Ascribe (something unpleasant)" , "Attribute or ascribe - say fault" .)