Indicated autographed correspondence is included (10)
I believe the answer is:
signposted
'indicated' is the definition.
The definition and answer can be both to do with communicating as well as being past participle verbs.
Maybe you can see an association between them that I can't see?
'autographed correspondence is included' is the wordplay.
'autographed' becomes 'signed' (similar in meaning).
'correspondence' becomes 'post' (I've seen this in other clues).
'is included' indicates putting letters inside.
'signed' placed around 'post' is 'SIGNPOSTED'.
Can you help me to learn more?
(Another definition for signposted that I've seen is " Clearly indicated".)