Former Arsenal winger Adrian Clarke has now claimed that Mikel Arteta needs to add one key ingredient to his squad this summer. Arsenal still have business to do before the summer transfer window closes. The Gunners have already signed Riccardo Calafiori, and secured the services of David Raya on a permanent basis following his loan stint in North London. However, Mikel Arteta still needs to bolster his squad in key areas. The Gunners need to strengthen their hand in the middle of park. Arsenal are pushing to sign Mikel Merino, but there are issues holding that deal up, as there are figures wi…