Autograph mail for an indicator supporter (8)
I believe the answer is:
signpost
'an indicator supporter' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.
'autograph mail' is the wordplay.
'autograph' becomes 'sign' (I've seen this in another clue).
'mail' becomes 'post' (synonyms).
'sign'+'post'='SIGNPOST'
'for' acts as a link.
Can you help me to learn more?
(Other definitions for signpost that I've seen before include "Wayside indicator" , "One may help you on your way" , "Route indicator" , "Direction indicator" , "Indication of direction" .)