Impersonation
noun, する verb
真似 is "impersonation." Actually, this word is too. It's also impersonation.
ものまね
The reading is 物 plus 真似 put together.
「いつも何してるの？」「毎日一日中物真似の練習をしてるよ。」
"What do you do every day?" "I practice impersonations all day, every day."