Peacenik competent for part of term (11)
I believe the answer is:
coefficient
'part of term' is the definition.
(mathematics)
'peacenik competent' is the wordplay.
'peacenik' becomes 'CO' (abbreviation for conscientious objector).
'competent' becomes 'efficient' (similar in meaning).
'co'+'efficient'='COEFFICIENT'
'for' is the link.
(Other definitions for coefficient that I've seen before include "Numerical multiplier of an algebraic variable" , "factor in expansion?" , "Mathematical multiplier (in an equation)" , "constant quantity" , "Factor that measures some property (physics)" .)