1. [v]  turn away from sin or do penitence
2. [v]  make amends for; "expiate one's sins"

ATONE is a 5 letter word that starts with A.

1. \A*tone"\ ([.a]*t[=o]n"), v. i. [imp. & p. p. {Atoned}; p.
   pr. & vb. n. {Atoning}.] [From at one,, i. e., to be, or
   cause to be, at one. See {At one}.]
   1. To agree; to be in accordance; to accord. [Obs.]
            He and Aufidius can no more atone Than violentest
            contrariety.                          --Shak.
   2. To stand as an equivalent; to make reparation,
      compensation, or amends, for an offense or a crime.
            The murderer fell, and blood atoned for blood.
                                                  --Pope.
            The ministry not atoning for their former conduct by
            any wise or popular measure.          --Junius.
   

2. \A*tone"\, v. t.
   1. To set at one; to reduce to concord; to reconcile, as
      parties at variance; to appease. [Obs.]
            I would do much To atone them, for the love I bear
            to Cassio.                            --Shak.
   2. To unite in making. [Obs. & R.]
            The four elements . . . have atoned A noble league.
                                                  --Ford.
   3. To make satisfaction for; to expiate.
            Or each atone his guilty love with life. --Pope.