Element of the code is just a stroke of the pen (4)
I believe the answer is:
dash
'stroke of the pen' is the definition.
'dash' can be an answer for 'stroke' (thesaurus). I am not sure about the 'of the pen' bit.
'element of the code is just a' is the wordplay.
I cannot quite see how this works, but
'element' could be 'as' (As is an example) and 'as' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for dash that I've seen before include "Hurry; destroy (hopes)" , "rats" , "Hyphen; small quantity" , "Daring" , "Small amount -- move fast" .)