Split school term for Christmas after one month (6)
I believe the answer is:
schism
'split' is the definition.
(I know that split can be written as schism)
'school term for christmas after one month' is the wordplay.
'school' becomes 'sch' (abbreviation).
'term for' suggests the final letters (the letter which terminates the word).
'after' means one lot of letters go next to another.
'one' becomes 'i' (Roman numeral).
'month' becomes 'M' (standard abbreviation).
The final letter of 'christmas' is 's'.
's' put after 'i' is 'is'.
'sch'+'is'+'m'='SCHISM'
(Other definitions for schism that I've seen before include "(Ecclesiastical) division" , "Split (usually in church)" , "Breach or division within church" , "Formal separation of a church into two churches" , "Difference in religious beliefs within a church" .)