I get into former head to atone for wrongdoing (7)
I believe the answer is:
expiate
'atone for wrongdoing' is the definition.
'expiate' can be an answer for 'atone' (I've seen this before). I am not sure about the 'for wrongdoing' bit.
'i get into former head' is the wordplay.
'get into' is an insertion indicator.
'former' becomes 'ex' (prefix meaning former or onetime).
'head' becomes 'pate' (humorous term for the head).
'ex'+'pate'='expate'
'i' put within 'expate' is 'EXPIATE'.
'to' acts as a link.
Can you help me to learn more?
(Other definitions for expiate that I've seen before include "Make amends for wrongdoing" , "Pay for" , "make atonement" , "Make reparation" , "Atone for (a sin)" .)