If you want to be invited, apply to the Editor (5)
I believe the answer is:
asked
'if you want to be invited' is the definition.
I can't judge whether this definition defines the answer.
'apply to the editor' is the wordplay.
'apply' becomes 'ask' (I've seen this in another clue).
'to the editor' becomes 'ed' (abbreviation).
'ask'+'ed'='ASKED'
Can you help me to learn more?
(Other definitions for asked that I've seen before include "Requested" , "Made a request" , "Enquired; invited" , "Inquired" , "Put a question to" .)