Makes up (for) (6)
'makes up for' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for atones that I've seen before include "Makes amends using a stone" , "Makes up for, say sin" , "Makes up for injury or offence" , "Makes amends for sin" , "Makes redress" .)
(Other definitions for guitar that I've seen before include "Plucked instrument" , "Stringed instrument, may be electric" , "Fretted musical instrument" , "Six- or 12-stringed instrument" , "Popular stringed instrument used by Beatles" .)