Again starts Religious Education, arithmetic, taking in English (7)
I believe the answer is:
resumes
'again starts' is the definition.
(to resume is to start again)
'religious education arithmetic taking in english' is the wordplay.
'religious education' becomes 're'.
'arithmetic' becomes 'sums' (mathematical sums).
'taking in' indicates putting letters inside.
'english' becomes 'E' (abbreviation).
'sums' placed around 'e' is 'sumes'.
're'+'sumes'='RESUMES'
(Other definitions for resumes that I've seen before include "Continues" , "Begins again" , "synopses" , "Carries on" , "summaries" .)