Writer records arms contractors (6)

I believe the answer is:
biceps
'arms contractors' is the definition.
Although both the answer and definition are singular nouns, I can't see how one could define the other.
'writer records' is the wordplay.
'writer' becomes 'bic' (Bic is a manufacturer of pens).
'records' becomes 'EPs' (EP is a type of record).
'bic'+'eps'='BICEPS'
Can you help me to learn more?
(Other definitions for biceps that I've seen before include "One operating arm" , "Flexor muscle" , "I bend the elbow" , "Large upper arm muscle" , "Arm workers" .)
