Blocks, last couple of five digits (6)
I believe the answer is:
vetoes
'blocks last couple' is the definition.
The definition and answer can be both to do with communicating as well as being verbs in their -s form.
Perhaps you can see an association between them that I can't see?
'five digits' is the wordplay.
'five' becomes 've' (I am not sure about this - if you are sure you should believe this answer much more).
'digits' becomes 'toes' (toe is a kind of digit).
've'+'toes'='VETOES'
'of' acts as a link.
Can you help me to learn more?
(Other definitions for vetoes that I've seen before include "Votes to block a decision" , "E votes to block decisions" , "Casts over-riding negative vote" , "Refuses to allow" .)