This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

n. one who helps or encourages or incites another

"And their biggest aider and abettor is Ottawa itself."

accessory    accessary   

fosterer    assister    coadjutor    compeer    roommate    answerer    predication    completer    shoulder-bag    handmaid