Mike and Heather enthralled by an advanced style of country music? (9)

I haven't cracked this one yet — but the brilliant team at Fifteensquared have:

[ M(letter represented by “Mike” in the phonetic alphabet) plus ( and ) ERICA(the genus of shrubs, including heather) ] contained in ( enthralled by ) [ AN + A(abbrev. for “advanced”) ].