the world > action or operation > behaviour > customary or habitual mode of behaviour > unaccustomedness or state of disuse > unaccustomed to [phrase] > out of practice (3)
one's hand is out: one is out of practice, or is lacking one's usual skill or ability at something. Now somewhat rare.
out of practice: without proficiency in a skill, through not recently having exercised it; cf. phrases 1b.