Reason for crack — paper over it in housework? (8)
I believe the answer is:
disunity
'reason for crack' is the definition.
'paper over it in housework?' is the wordplay.
'paper' becomes 'sun' (The Sun, UK newspaper**).
'over' says to put letters next to each other.
'in' is an insertion indicator.
'housework?' becomes 'diy' (do-it-yourself work, work done on one's house).
'sun'+'it'='sunit'
'sunit' going into 'diy' is 'DISUNITY'.
(Other definitions for disunity that I've seen before include "Lack of oneness" , "Lack of solidarity" , "conflict" , "Lack of agreement" .)