Summons is written up, action it! (8)
I believe the answer is:
citation
'summons' is the definition.
(citation is a kind of summons)
'up action it' is the wordplay.
'up' is an anagram indicator (letters get chucked up).
'action'+'it'='actionit'
'actionit' anagrammed gives 'CITATION'.
'is written' is the link.
I am not very happy about this link. Some or all of it may belong to another bit of the clue.
Can you help me to learn more?
(Other definitions for citation that I've seen before include "Mention in an official report" , "Official recognition of achievement" , "Award usually given as formal public statement" , "Mention; quoted passage" , "Encomium, tribute" .)